Thanks for the feedback. It seems that their performances do drop after a season or two, despite being young players and fast trainers; a typical Nordeus tactic.
So far, not very convincing as you can still get close too, equally, and even better performing players from both the auction market and the scouts' list. The main advantages is not having to pay the transfer market value fee, and avoiding the hassle of keeping an eye on the transfer market very frequently for particular players.