i term good players 4/5 stars(25-29 being 4 stars), which is mostly what i have. Ive 2 scouts, one who will become legend very soon. I also have 2 3 star players who are young and progressing well.
Ive a few older, better rated players who were cheap and although they wont last long theyll do a job for a few seasons and were easier to aquire, during this time i can train my younger guys up to replace them when i sell them (I will do this before they retire, letting them retire would be a waste). For me personally i buy n sell fairly often, always looking for better than what ive got, so age isnt really an issue.