Just turned 29, been capping seriously/smartly for about 5 years (although I bet on sports like an absolute moron for 4 years prior to that). I really have learned some valuable life lessons during all of that, so I wouldn't trade it for the world. I absolutely love the challenge of beating the books consistently and will probably do it until the day I check out (so I better not go broke before that).
Here's a bit of a twist to this question: anyone remember the first serious sports bet they ever made? I was 21, in college, and bet $25 on the Cowboys -3 @ Chicago on opening weekend MNF. I paced around frantically like my whole life depended on the outcome, yet nowadays I sometimes doze off during games I have over 10 times that amount in action.
(btw, I lost that Cowboys bet).