Training - Skill Decline

[howie123]

Hi

Was wondering if there is some player attribute that governs how long a skill stays at its max level before it starts to drop ?. Reason I ask, is that I have a 20 year old player who's skills keep dropping from their max level at a quick rate (like every few days) and I'm constantly having to tweak his training to keep whichever skill it is at the max level.

Thanks