I'm still not going to say exactly where I'm going athletics-wise, but I'll point in the general direction... that way (man, I am so funny).
Over the last year I've read a bunch of books about endurance sports training. Interestingly, two of them (Swim Coaching Bible and Daniels' Running Formula) focus on training youth athletes. The important message was not to start with too much -- volume, intensity, specificity, etc.
I have this buddy who, seemingly on a whim, ramped up from zero to marathon training a little over a year ago. He's also got an ongoing, consistent string of injuries.
My take away here is that actual age doesn't reflect "athletic age" (I didn't make that term up, I swear -- sports scientists much smarter than me have been using it for years). The problem with so many "non-youth" athletes that start as masters or return to sports after a long lay-off is that they want to go after the big events (marathons, Ironman tris, century bike rides), despite being effectively "infants." Jumping straight into marathon training works for a lot of people, I'm not going to deny that -- and if it makes them happy, that's great. But if you're constantly injured, I'd wager your body isn't ready for the training stress.
So what does that say about me? I've been pretty lucky over the years, injury wise. A likely reason is my athletic age is probably pretty close to my actual age -- I've been swimming, or rowing, most of my life.
That said, I do have some recurring injuries related to my achilles, likely because my "impact sports" athletic age has me still in diapers. Those problems have only come about since I've been training for the long stuff, so, the direction I'm pointing right now --> no long stuff until I get this worked out.