When you are left with no player with a contract, unknown players 32-34 years old are added to your team

So you can keep a 3* team all the season all the seasons without issues (they don't grow much with training )

From my Experience, from Bronze 3 to Gold 3 is very easy to Win tournaments also with 3*, in Gold 2 is also easy albeit a bit less, in Gold 1 real competition starts, Platinum I do not even try because it's very very hard with 3*