I'm 22, riding a 27-year-old CB650. Wow, I didn't realize the bike was that old 'til this thread came up. I guess that would explain some of the problems I've had. Running good now, though!
IMHO you're not over the hill 'til you hit 55. Then it starts going down, and you're by no means done for!
My dad's 54 and my mom's 53, still raising an 8-year-old daughter (youngest of 9). I'm right in the middle.