The young expensive guys (what is called gens on here) can keep up with a regular team for a long time, several seasons. I have a guy that just turned 3* this season that started with my 35T team:

Click image for larger version. 

Name:	murray.jpg 
Views:	44 
Size:	78.5 KB 
ID:	31546

He'll likely get his 4th star back this season, too.

What I try to do is have a core best 11 that are faster trainers, and replace a couple guys a season. Good players that are slower trainers have to play every match and get a booster training every so often to stay in my Team longer.