Riding Losing It's Marginal Benefit

For somewhat of fun topic, I ran into the press conference of Lance Armstrong announcing his retirement from cycling after the 2005 Tour de France, win or lose. With such a competitive spirit and an inspiration to millions (LIVE STRONG!), how did he weight such a decision. Perhaps like everything, there's a declining marginal benefit. After breaking the all time winning record, perhaps the sweet smell of victory isn't as strong for Lance anymore as he'd like to focus more on his kids and of course...... Sheryl.

I'd like to look at this situation graphically with utility measured vertically and as a function of wins. As you keep winning, you get hungrier for it and it consumes you. But, at a point, the benefit reaches a maximum and utility decreases with each additional win. The decrease in utility could stem from time away from family, lack of incentive, or the aging process.

What's your opinion?