Cork, like felt and leather will compress together if the drag is left tight in storage... When that happens you get two results... You lose the range the drag had - and it gets sticky... Both are bad outcomes and one of the reasons that many reel makers have switched to carbon fiber or similar synthetic materials for their drag washers....
Always back your drag to zero when storing any reel - fly , spin , conventional. You'll greatly extend the life of a drag system that way....
By the way I can tell at a glance when tearing a reel down for repair/maintenance whether the drags have been locked down in storage - it's pretty obvious....