How on earth do you manage to keep them so long? I've got a whole roster of fast trainer Nordgens that produce very well for me but several are now 20-21.

My understanding is that they slow down in growth at 21 and I am promoting every season. Can I really grow them a star per season after 21 or will they still play well if not?

I hear people say stars mean nothing but my trophy case seems to disagree (I have 2 cup titles and 2 league titles in 3 seasons as well as 2 CL final losses and a 2nd place league finish).