Géza Vermes, professor emeritus of Jewish studies at the University of Oxford, is a world-leading authority on the Dead Sea Scrolls and the background to the New Testament.
By the time his latest book, Christian Beginnings: From Nazareth to Nicaea, AD 30-325, is published in July, he will be 88.
Zygmunt Bauman, emeritus professor of sociology at the University of Leeds, which has an institute named in his honour, remains equally active at 86.
Since his retirement in 1990, a stream of books about consumer society and what he calls "liquid modernity" have seen him acclaimed as one of the country's leading sociologists.
The end of his university career, with distractions including "endless and exhausting, yet barren and eminently forgettable, brawls and squabbles in and out of committee rooms", Professor Bauman once told Times Higher Education, enabled him to do much more of the curiosity-driven research that had brought him into the academy in the first place, but now "unimpeded, uninterfered and untinkered with".
These are just two striking examples of the ways that emeritus professors can continue to produce important work - and to contribute to the reputation of their universities - long after they could have put their feet up.
But what help and encouragement do scholars' former employers give them to keep research-active?
That was the question that Angela Thody, herself an emeritus professor at the University of Lincoln's Centre for Educational Research and Development, set out to answer. The results were recently published in the journal Studies in Higher Education, in a paper entitled "Emeritus professors of an English university: how is the wisdom of the aged used?"
It drew on a survey of 71 emeritus professors at an institution given the pseudonym "Borchester University" for the purpose of the study.
The difficulty Professor Thody encountered locating those academics, she suggests, may say something about how they are regarded. "The few, scattered direct emeritus references on the university's website showed the challenge for those seeking seniors' expertise," she writes.
One reader with whom she corresponded was unaware of his own emeritus status, she adds.
After contacting the institution's 71 emeritus professors, Professor Thody received replies from 31. Of these, 26 were still publishing in academic journals, 25 reviewing articles or books and 11 serving on editorial boards.
Although their work was unremunerated, 21 were completing pre-retirement research projects and eight had embarked on new ones.
The pattern seemed to replicate what earlier researchers in the UK and US had found - that for 10 years after retirement, most emeriti remain academically active, with a tailing-off of activity thereafter.
As to the quantity of research they generated, Professor Thody's small sample was split three ways between those producing less, more and roughly the same amount as before retirement.
One says he felt he was doing the best work of his career, while another shared Professor Bauman's delight that release from teaching, bureaucracy and departmental research priorities permitted the scholar to "devote myself full-time to research which I can control to my satisfaction and in directions I consider are most important".
Such a licence to roam more widely is reflected in Professor Thody's own career.
"Up to my retirement," she recalls, "I had to concentrate publications on my own discipline [of educational leadership] if only to meet research assessment exercise requirements".
Emeritus status has enabled her to explore more historical themes, different ways of writing and presenting research, and the challenges for emeritus professors considered here. For many academics, retirement means freedom to work rather than freedom from work.
The university seems to play a very limited role in all this activity.
Many of the emeriti questioned self-funded their research. Although 11 of them had publications that formed part of Borchester's submission to the 2008 RAE, five were submitted for other universities.
"The v-c at my retirement made much of his desire that I should remain research-active," one comments, "but I have found it more convenient to continue research with colleagues no longer at Borchester."
This statement reflects a general view that the university had little awareness of their specific needs.
A science emeritus reports doing "a lot of unrecognised work for the department in supervising, mentoring, etc. I am also an active conference organiser, etc. It would be in the university's interest to pay me a modest stipend - but they don't."
Another says: "Why would I stop doing academic work? It is ongoing and I love it. The department also needs the continuity. Our graduate students certainly do."
Unfortunately, since "consideration of the individual situations of emeritus professors is totally lacking" within the university, the respondent had to take up an overseas appointment for financial reasons.
Generational solidarity celebrated
This year marks the European Year of Active Ageing and Solidarity of Generations, which Lazlo Andor, the European Commission's commissioner for employment, social affairs and inclusion, hopes will "act as a catalyst to mobilise citizens, stakeholders and decision-makers to take action to promote active ageing, tackling the challenges of ageing in a positive way".
Many academics, as Professor Thody's research shows, are only too eager to pursue the opportunities of "active ageing".
Yet former employers and funding bodies show few signs of wanting to capitalise systematically on this, with support frequently being haphazard or opportunistic.
In her own case, for example, Professor Thody "happily retired at 60 in 2003 and then, as the staff in my old department departed to other jobs, the v-c asked myself and a colleague to return for a few months to look after the doctoral students in education while new staff were appointed. They were all in place by 2006-07, but the department then expanded so quickly that we were still needed - so I am there now with 17 doctoral students to supervise."
When she put in a bid for a Leverhulme Emeritus Fellowship to continue the research published in her Studies in Higher Education article, however, she was unsuccessful. "It was not a continuation of work begun before retirement, which is a criterion for the award, so that means that there are no funds for emeriti who could develop new areas."
Asked for further details of his recent work, one of the Borchester emeriti cited in Professor Thody's article says he has been "more prolific since retirement (and I had a pretty good [publishing] record before that)", partly because of having more time and partly because of "no longer being so angry all the time about what was going on in the universities".
He adds: "Getting right away from all this has made it easier for me to think about my research if I wake in the night, rather than fume about the latest idiocy in higher education.
"The RAE never constrained the sort of research I did before my retirement and I have just continued writing the same kind of books since."
Although he says he is unsure whether the university has gained any prestige from his publications, this seems unduly modest, given that he "recently had an approach about the possibility of re-employing me so it can include me as a member of its Category A staff for the next REF".
The good news for both individual scholars and the growth of knowledge, concludes Professor Thody, is that "about half of Borchester's emeriti remain very happily active in teaching and research".
Yet given that they are "not always remunerated for it, incorporated into research ratings returns or recognised by the university for it", it is more than likely that other academics have either thrown in the towel or taken their expertise elsewhere.
It remains a crucial challenge for universities to help many of their emeriti build what Professor Thody calls "flexible second-life careers".