With most banks those pre-authorizations fall off your account in three or four business days if the charge has not been finalized. I regularly see this happen when checking in for five night stays with my Chase card. About the day I check out the pre-auth has automatically fallen off and then a couple of days later the actual charge appears.

I've been lucky I guess. Never have had a hotel authorize for more than about $20 over the room rate and tax and never have had a car rental company (I stick to just Avis and National) do more than the rate for the car and tax times the number of days on the contract.