As an old T11 manager (this season is the 43rd and still not tired of this game ), I have experienced the old T11 where there weren't skill points yet. So, when they changed it and put skill points, those times players gained almost the double % of how they do now.
One day I found this striker 18 years old that could gain 200% in every official game (like 8% for every 1% of physical condition).
So, I decided to spend a lot of green bags to train him as much as I could. (not a single cent spent. Only tokens from videos.)
The result?? I kept him like till 30 years old (12-13 seasons), If I'm right.
During that period I won the league every single season, so imagine how many skill points he gained in all his career for keeping him so many seasons.

If I had 45 games (average) every season, he must have had 540-585 appearances.
Let's say 500+ to be sure.

Obviously I can't prove it, because it was long time ago and it's not reported in the history of my team.
Anyway, that was my best player ever. Good times.