Just the fact that we're all on a forum about actively riding bikes means that our physical age is far younger than our numerical age. I work with a bunch of 20 through 50 year olds and work and they are usually in awe of my bicycling achievements (latest, the 130 mile Markleeville Deathride). I look a lot younger and fitter than some of them too! I am a complete subscriber to "you're as old as you feel". I may die sooner than they do but I'll certainly leave a much better looking corpse.