The maths aren't difficult. Academics who began their working lives in the 1960s are now retired or approaching retirement. The era's student activists, many of them postgraduates at the time, may still have leadership roles as departmental chairs and senior administrators, but they too will be leaving the academy soon enough.
What sort of loss will this represent? Will they take a distinctive set of values with them? Have they left behind an important legacy we may still draw upon, or simply a set of touching ideals that lost their relevance long ago?
"I'm pretty sure that academics like me feel blessed to have been alive and young in that dawn compared with the way things are today," says Leslie Gofton, who lectures in the School of Applied Social Sciences at Durham University. "But it's hard to talk to postgraduates today about 'the way it was' without sounding wistful, sentimental or just a bit patronising."
Although "the past always gets a better rep than it deserves", Gofton says, he remains convinced of the continuing relevance of an era when "suddenly loads of stuff was up for grabs, which never had been before, or so it seemed - from the length of your hair to your sexual preferences".
Although he and many of his cohorts went through a more sceptical phase when they saw the Sixties as "a time filled with youthful delusions and (the) mistaken analysis of society", he now takes a far more positive line.
"Strange to say, I actually feel more comfortable now, given recent events - capitalism discredited, Obama rising from the abyss. Maybe all we really need is love."
Of course, that decade did not usher in an era of universal peace and love. Even in San Francisco people are no longer sure to wear flowers in their hair. Despite the changes in relationships and individual freedoms, many things have gone on much as before.
In the words of the late historian Arthur Marwick: "There was no economic revolution, no political revolution, no advent of the proletariat to power, no classless society, no destruction of mainstream culture, no obliteration of language."
So what is there to celebrate and hand on after all these years? Fred Inglis, now emeritus professor of cultural studies at the University of Sheffield, graduated from the University of Cambridge in 1960 and spent most of the next decade as an academic.
"There were thrilling posters everywhere. Things like 'Imagination Rules, OK?' Now it's a cliche, but then it was dazzling ... There were more committed students than at any other time. Never before or since was there such a sense of keen exchange."
Changing attitudes to sex and drugs, he adds, "seemed very sudden. I say that in no lip-smacking way, because I had done the traditional thing, got married at 25 and had small children.
"But on campus the change was sudden and widespread - you weren't thrown out of university for sleeping with the opposite sex! Universities quite quickly adapted to that. That seems an unqualified good."
Inglis continues to regard the ideals of the Sixties as a standard against which to judge today's universities, which are often found wanting.
"Corporate thought now runs the show - if the voice of 1968 were more alive there would be more criticism of managerialism and universities having to make money," he says.
"Students are given a programmable body of knowledge without it becoming part of their identity. It's now a question of handling knowledge at a distance, as an instrumental tool of social mobility, rather than making it part of one's identity.
"It's the technologising of thought. It's the teacher saying 'Here's how to get a 2:1' rather than 'These things matter intensely and can be found in these books - which you need to absorb by tomorrow.'"
Certain younger academics, who feel they grew up in the afterglow of that tumultuous decade, continue to write about the period with passion and commitment (see box, opposite). But the fact remains that the Sixties are fast becoming social history and the major participants are slowly but surely departing from active professional life.
So what are the decade's useful legacies? For Richard Flacks, the main treasures that Sixties academics are handing down to their successors are the universities themselves.
Now 72, Flacks is research professor of sociology at the University of California, Santa Barbara, and author (with Jack Whalen) of Beyond the Barricades: The Sixties Generation Grows Up (1989).
Although the people he writes about, he says, were "once accused of trying to destroy the universities", in reality they have proven crucial in keeping them alive.
"A great many took responsibility for sustaining institutions of higher education in the face of corporate encroachment, declining budgets and other threats. The Sixties generation who became academics were among those who most staunchly defended universities while striving to make them live up to their stated aims.
"And their positions and practices were far less radical than one might have expected 40 years ago, or that the right-wing scare about 'tenured radicals' would suggest."
Flacks seems broadly optimistic about a future in which, along with more women and minorities in leadership positions, "we may see a renewed state investment in science as the processes of globalisation continue to transform the curriculum".
He thinks that it is largely down to the Sixties generation that universities are still in reasonably good shape to profit from these opportunities. That is their gift to posterity.
Flacks was one of the founders of Students for a Democratic Society (SDS), a leading "new left" activist movement that lasted from 1960 to 1969. It is a sign of the times that two high-school pupils opposed to the Iraq War and committed to participatory democracy decided to resurrect the movement in 2006. One of the first things they did was contact surviving members of the original SDS.
But what of the lifestyle changes and the student radicalism of the 1960s? Were they signs of a better society, high-spirited irrelevance, a cosmetic change in middle-class behaviour or the beginning of the end for Western civilisation?
These questions remain disputed, even among those who took part, some of whom have shifted across the political spectrum from anarchist to arch-reactionary.
Speaking on "Women's Sixties Renaissance" at a "critical celebration" of 1968 last year, Lynne Segal, anniversary professor of psychology and gender studies at Birkbeck, University of London, suggested it is precisely these arguments that make the era important and relevant today.
"The legacies of (the 1960s) live on," she says. "They persist if only because they remain so fiercely contested - the Sixties spirit is as precious to the libertarian Left as it is anathema to the Right."
For example, President Nicolas Sarkozy has claimed that his bold plans to renew France will "do away with May '68, once and for all". Anything worth attacking in such terms must have something going for it.
This "Sixties spirit" has proved hard to define, never mind bottle, for posterity. But Segal, like several of her contemporaries, has recently turned to reminiscence to try to sort the wheat from the chaff in her radical past.
One of the key issues about the Sixties is the appalling sexism prevalent back then. Segal was the UK's first professor of gender studies and her lecture on 1968 recalled women depicted as "buxom pneumatic chick[s]" in "countercultural radical porn", or as "masturbatory aids and sources of male bonding for those busy drafting or eagerly absorbing outlaw manifestos".
More inclusive and informal styles of political debate often led to women being shouted down or subjected to lewd abuse. Sheila Rowbotham, emeritus professor of gender and labour history at the University of Manchester, found herself "an object of derision" when speaking at a British student rally in 1968: "It was like a living nightmare. Stubbornness kept me in front of the microphone ... Somehow through the whistling and laughter I managed to speak about (the underfunding of) further education."
Kay S. Hymowitz, William E. Simon fellow at the Manhattan Institute, recalls other typical scenes: "The 'big man on campus' in 1968 was carrying a volume of (revolutionary writer) Frantz Fanon instead of a football, but he still had his pick of women whom he could discard at whim. The difference was that now they wore miniskirts and were willing to put out. That world turned out to have its own strictures, including that sex was a natural and easy pleasure with no important differences on that score between men and women.
"A friend at Berkeley at the time remembers that at political demonstrations men would yell, 'Chicks up front!' They knew that the police would shrink from bashing female demonstrators' skulls, while they themselves could march on, free of all chivalrous demands."
Such attitudes soon generated their own reaction. Segal recalls one of the slogans at a meeting of the Socialist German Student Organization in 1968: "Liberate socialist eminences from their bourgeois cocks."
So what does Segal think she is handing on to today's activists as she reaches retirement age? She devoted a book, Making Trouble (2007), to remembering her life as a radical. She recently recalled her first political engagements.
"At sweet 17 - well, probably not so sweet, but certainly naive - I first encountered the heavy arm of (an) Australian state determined to stifle my youthful anarchist leanings, which I imbibed from a group of local bohemian radicals known as the Sydney Libertarians.
"My first - and, thankfully, to date last - political arrest was for flyposting our principled abstentionism: 'Don't Vote! Whoever you vote for, a Politician gets in.' We plastered the posters on public hoardings, our message illustrated with three little pigs, poker-faced, bowler-hatted, arms crossed."
Today, Segal is aware of the weaknesses of a style of politics that refuses to engage with the state. But she also notes that "the old, permanently distrustful, pessimistic anarchism that I briefly embraced in (the) bohemian Sydney Sixties is back in fashion in certain academic circles today".
In this light, she mentions, for example, the views of Simon Critchley, now part-time professor of philosophy at the University of Tilburg, in books such as Infinitely Demanding: Ethics of Commitment, Politics of Resistance.
Segal wants to celebrate the continuing relevance of the Sixties' "open, pluralistic forms of dissent", which have inspired "many indigenous, anti-war and anti-corporate globalisation movements". Despite that decade's naivety, self-righteousness and sexism, she believes there is also a valuable inheritance to draw upon.
Student unrest in Sixties Britain was relatively mild and contained compared with events in France and the US.
Academic, journalist and Times Higher Education contributor Laurie Taylor remembers there was an element of bathos in the protests seen at his stomping ground, the University of York.
"Maybe students at the Sorbonne or the London School of Economics were complaining about the mechanisation of the university and how it was producing cogs for the great machine of capitalism. At York it was about the increase in the price of coffee in the snack bar.
"While we were marching with lit torches across the croquet lawn to occupy the administrative building, we were led by a 'Tankist' (someone who joined the Communist Party when the Russian tanks rolled into Prague in 1968). The rest of us were all fooling around, having a laugh, half-pissed and asking who had the spliff, and suddenly he turned round and shouted 'To the Winter Palace!' It was to the credit of most of the students that they fell about laughing."
Some have dismissed what happened at the LSE as small beer, too. Michael Zander, emeritus professor of law there, has strong personal reasons for remembering the protests of January 1967 following the appointment of a new director, Dr Walter Adams, because of his links with Ian Smith's regime in Rhodesia.
A meeting held in defiance of the outgoing director's instructions resulted in the accidental death of a porter from a heart attack. Disciplinary hearings followed, where Zander defended one of the students. When some were suspended for a few weeks, it led to the famous sit-in.
"Since this was the first major bust-up in a UK university (and the LSE is located near Fleet Street), the events were widely covered in the press. I made a speech at the students' union, then almost permanently in session, which was designed to calm things down.
"I said the sit-in had been a great event but that now was the time to bring it to an end. Newspaper reports missed out the second half of my statement, so I got into trouble for apparently egging the students on."
Zander remembers the "very heady and feisty" debates, the "ructions and bad feeling" among staff divided on "issues that seemed tremendously important at the time. But although students won their right to representation, they didn't always make much use of it. It was all a bit of a storm in a teacup.
"Students disrupted the LSE for a few days, although some departments made arrangements to continue teaching outside the university. But then things went back to normal with only a few minor changes."
Within the LSE's law department at least, the long-term impact of the UK's most famous student sit-in was pretty much zero.
An observer from another discipline, however, thinks the events had a lasting significance. Stanley Cohen was a graduate student at the LSE from 1964 and 1967 and is now emeritus professor of sociology.
He was already working on a PhD examining the clashes between Mods and Rockers in English seaside towns in 1964.
His research was a classic example of participant observation, since, he has written, he "wore what could be called Mod clothes and enjoyed the days with various groups on the beach and the nights at the clubs".
Observing the fights, he says, was "more amusing than frightening", and the scale of the violence was vastly exaggerated in overheated press reports and magistrates' comments.
The discipline of sociology, deviance theory and Cohen's crucial notion of "moral panics", since applied to everything from football hooliganism to tales of satanic abuse, rank among the notable intellectual legacies of the 1960s. But the sit-in, he believes, was not only "exciting and important" at the time, but part of wider international struggles against the Vietnam War. Similar demonstrations at institutions across the country, including the LSE, have recently returned in response to the Israeli assault on Gaza.
There may even be veterans of 1967 who are still active enough to take part in today's protests. The outgoing Sixties academics are not just survivors of a long-forgotten party, but leave much of significance behind.
A CAUSE AS WELL AS A DECADE: THE SIXTIES VIEWED TODAY
As the Sixties generation leave the universities, their experiences are becoming the stuff of social history. Last year saw the creation of a new journal called The Sixties (Taylor & Francis), edited by three American academics born between 1964 and 1970: Jeremy Varon, Michael S. Foley and John McMillian.
Now that the passions of the past are officially a matter for academic analysis, one might expect them to be dried out and dissected. But although the journal is subject to the rigour of peer review, it is striking how much "the Sixties" remain a cause as well as a decade.
A journal of Crusader studies would be unlikely to feature a partisan editorial expressing support for the Christians or the Muslims, but Varon, Foley and McMillian know which side they are on. Although they deny any simplistic feelings of nostalgia, their first editorial admits to "a more discerning kind of affection for a past that is not properly our own, but with which we nonetheless feel a powerful, if complicated, affinity.
"We were too young to have been fully in the thrall of the Sixties, but just old enough to know that we missed something big. Burdened with the sense of having arrived too late, we spent much of our early lives nourishing ourselves in the era's afterglow and trying to affirm, in ways political and personal, what we saw as its best values and impulses."
Varon, associate professor of history at Drew University, adds that he and his fellow editors were careful not to co-opt too many "veterans", because they didn't want "to give the editorial board the quality of a 'reunion'". But he adds: "Younger folks who write about the period tend to feel, in my observation, a tremendous sense of affinity with the basic values and goals of the era's signal movements, and are strongly motivated in their research by political and moral concerns. 'Detachment', therefore, is not 'disinterest'."
But what will it mean when the last Sixties academics give up teaching and writing? While this would obviously be sad, Varon replies, "the movements of the 1960s so massively transformed academia that the influence of the era remains strong: in the fundamentally critical nature of all disciplines; in a bohemianism that still defines, to an extent, the liberal arts; in traditions of campus activism; in diversity, pluralism and expanded access to higher education; in the quest for relevance; in the relaxation of institutional and generational hierarchies; and in a conception of college as a time for existential discovery and ceaseless questioning. So the 'spirit of the Sixties' does not necessarily depend on the presence of folks from the 1960s."
Handing on the baton he has inherited, Varon says he strives to act as "patron (humbly) for the students who protest against the Iraq War, Guantanamo, etc".
How long did the Sixties last? This sounds like a stupid or purely academic question, but many have argued that some of the things for which "the Sixties" is shorthand were actually linked to a longer period, lasting from roughly the mid-1950s to the mid-1970s. This is sometimes known as "the long Sixties".
For example, if the Vietnam War was the central Sixties event for Americans, the conflict's crucial limiting dates are the Geneva Accords of 1954, which ended French colonial rule in Indochina, and the fall of Saigon in 1975.
Whatever the merits of this idea, it has the effect of widening the range of people who can claim the Sixties badge.
Dr Gerd-Rainer Horn, senior lecturer in 20th-century history at the University of Warwick, has written a book called The Spirit of '68: Rebellion in Western Europe and North America, 1956-1976 (2007). Although he was born in 1955 and became politically aware in the early 1970s, he goes out of his way to redefine the Sixties as something he was part of.
"One could easily regard the 20 years between 1956 and 1976 as one long mobilisation cycle," he argues, "which, certainly in some countries, had a highpoint in 1968 itself, but which continued into the 1970s.
"Indeed, I would argue that the spirit of 1968, however one may classify it, had a much more substantial breadth and depth in the first half of the 1970s than in the late 1960s.
"In other words, far more people were affected by that (elusive) 'spirit' in the early years of the 1970s than in 1968 itself. So in that sense even people like me who came of age (politically) in the early 1970s were actually products of the spirit of '68."
As long as the Sixties remain contested or form the sort of club people aspire to be part of, we will continue to live in their afterglow.