I've heard stories of hooks being sent for recondition and returned with no apparent evidence of anything done to the hook.
But it does come back with an EASA form and an invoice
A CG hook comes in handy as you can use the back release for ground retrieve; so, theoretically only two operations per aerotow flight -- release check and release in the air.
Well, that's provided the hooker up knows how to do the back release; so. four per flight.