I guess I'm older than when this thread started .
56, heading toward 57 in the fall. I started riding at 47. I did a lot of riding as a young teen and a bit of neighborhood/riding to university stuff in my twenties and early thirties.
I've seen some changes in my ability to recover, but my fitness is still pretty good... I don't really train, per se, although my overall endurance has definitely improved this year from just more time on the bike and lots of winter endurance activity. I know I could improve my ability to sprint and maintain a higher speed on the flats, but I am too lazy! On the whole, though, I wish I had started to do this type of riding in my twenties or thirties.