Don't get me wrong, I thoroughly enjoyed my time, I might have been unlucky on this occasion as the group I was with just wanted to drink tea all day and not go out and explore, finally retiring for bed at 2000 hrs. I'm very active (mid 40's so not a spring chicken myself) enjoy getting out and about.
I find this very puzzling: presumably this was a "stay put" holiday somewhere? I can well imagine that this might attract sedentary types - of all ages.
I tend to travel independently in Europe and use a group for long-haul tours in Asia: in my experience it is physically impossible to get to bed by 20:00 if one has been travelling or sightseeing all day! Such tours tend to attract interesting people with enquiring natures who are good travelling companions throughout the day, and of whom some like to sit in a bar until late while others like to go out after dinner and explore (Asia after dark can be very interesting) - and some do both! But age was never a factor.
On an actiive holiday, there can of course be good reasons for retiring early on at least some nights: the effects of jet-lag, long days travelling and sightseeng, and the need for unnaturally (for me;-) early rising on some days can all take their toll. And don't forget that some people - of all ages - are naturally awake very early so go to bed earlier: they may take a dim view of those of us who usually stayed up late, but they were always too polite to say so.
As regards age, I went on a tour round China last year with a "solos" holiday company (not with JY) and met a very interesting man who told me that, being nearly 75, the only thing which would stop him travelling would be the rising cost of travel insurance: he had recently spent two weeks touring independently in India, and had managed to extend his China tour (ending in Shanghai) with a private add-on to Hong Kong. He was also the only person in our group who regularly went swimming in the hotel pool before breakfast - and he didn't go to bed at 20:00 local time . . .
Again, I have a Scottish friend whom I meet regularly several times a year in Munich and Leipzig (don't ask . . .). He is nearly 76 now and after a full day with friends (usually spent practising our schoolboy German:-) we usually stay up late quaffing ale in the hotel bar until well after midnight because he is a good conversationalist and we have so many interesting things to talk about - and then he usually gets down to breakfast before me, having been out to try and buy an English newspaper . . .
So, it is probably neither when you go nor the age of your travelling companions which is important, but where you go, and with whom . . .
Good luck at Christmas - but do try a long-haul touring holiday!
Jim