I don't believe there is any reason other than health issues that should make a good pool player that still puts quality time into his/her game peak at the age of most other sports. I think with most top tier players that quit, it's because they get tired of the grind for the little money in return. Keeping that killer instinct for 30, 40, or 50 years is tough. Making the game 4 to 8 hours a day of your life for all those years is also hard to do. Johnnyt