[@Holy Soldier] - I believe one way might be to have the learnt effects fade over time to a base level dependent on overall exposure and time since last exposure.  The more exposure, the slower the learnt effects fade.  And maybe a delay from exposure to ability increase effect, so he's not instantly able to counter.  And the more incidents, the higher the resting base level.  How this would be actioned in game, I have no idea, but that would appear to sort out both issues.  I'll leave this as a suggestion for [@Sarcelle Renard] to put some thought into.