Originally Posted by Firewind

A version of this has always been the huge advantage of Hertz #1 Gold at airports. You reserve the car for a certain time. The contract hanging on you rear view mirror has an "Out" time three hours after that, and that's the time that remains on it. Probably two reasons they do it: Competitive advantage, and the operations research principle that it's more efficient (cost effective) to avoid all the effort of sweating the small stuff viz airline delays etc.