As I've said in ma team showcase page I had 3 players that leaved the club due to age, 33 or 34.
I will suggest to create the option to pay some tokens to keep players during more years, like unlock the age
35 for, 12T
36 for 18T
37 for 22T
38 for 24T
This till 42.

All managers have this special player, 1 of every 30 or 40 that they wanna keep till years so, I think is a very interesting idea, because at the end these players are slow trainers, and managers will keep these only for fun/special feeling for them.