Players can reitre from age 32 to 34. Untill you players is under contract he cant retire if you go under your player detail info you can see under contract how many yeras your player still have left to play. The onyl way you can lose this playr is by going into bank balance in minus and game sells him after 7 days or you sel him.

My tipp. Buy your self a player aged 18 at the start of the new season make sure he is a fast trainer you can see this by compering his market value to other same aged players and buy 4 or 5* players. Those players you can keept in you club form more than 6 sesons if they are good. I bougt my best player 3years ago with value of 18 milions and quality 53 now after 3 seasons hes value is 26 milions and quality is 67 hes 6* or a scout now form me I thin Ill keept him as long as he wont drop under 4*.