I have had couple of players between 33 and 37. The drops in skill were between 2 and 5 per season.
The only thing looked that if I played them normal minutes, the drop went slower than if I just used them when I needed them for minute management.
The highest skills seem to drop earlier than the lower skills.
It is a risk, salary wise, but I believe the high experience is a nice compensation.
Only in the dark, we succeed!