There are a number of factors which determin the longevity of a pro bodybuilder.
First and formost, would be success. Winning or making money from the sport, is essential to continued interest and participation as placings fall off/ contracts arent offered/ so goes the lengh of career.
Finances would be next on the list, as bodybuilding is not cheap...and eventually, paying the bills takes priority.
Third would be maturity/ priority in life...as the pro gets older, family and future become more of a reality and a decision has to be made to regroup and move on.
Well said! Thanks for the answer.