Completely non scientific theory, although inspired by McGilchrist's "The Divided Brain" I'd wager that as we age the left hemisphere takes more and more of our awareness as we map the world internally and we tend to live more and more from "what is already known" as opposed to present experience.
I too have hundreds of hours of meditation and I remember the feeling of time was very much affected. One night I remember out of sheer stubborness I sat for 5+ hours and I always remember the next week felt like it was a month.
It doesn't have to do with having "new" experiences, or new memories, or doing anything "interesting". It has to do with how we attend to the world.
And as Gilchrist pointed out this is being worsened as the devices we use day to day like smartphones, which aren't inherently bad, tend to stimulate mostly the left hemisphere unless you just listen to music. All the time you're going after buttons, notifications, looking at the icons, you're just continually sucked back into the world of the left hemisphere : icons, words, symbols, "things" to do or that could be done, things that could happen, emails, posts, likes, whatnot.
Actually I think it was already shown through EEGs that long time meditators, buddhist monks, had some areas of the brain more developed.. which would seem to support my theory likely those areas are related to the right hemisphere (and hence the right hemisphere's qualities such as ability for compasssion, seeing the whole, seeing things in context, ... and therefore seeing one's life in context as well instead of an old tape repeating in your mind everyday).
edit: also if you think logically, then it makes sense that the common intuition that having new experiences, or adding more variety in your life would make time feel like it goes by slower, but it is not because of "new" experiences, but as in my theory above, because those new experiences stimulate the right hemisphere, as you become more focused and attentive to what is happening NOW. In fact by definition any new experience will stimulate the right hemisphere. So if you dont have the $$$ to go out and enjoy the world, or take a vacation the good news is you'll probably enjoy the benefits of right hemisphere activation by doing... NOTHING! (ie. meditation, focused attention on the breath or any one of many techniques all revolving around developing concentration and attention) :)