However, many rates also have a min/max or other triggers (Sat overnight keep, etc). If you book through Avis.com, on the 4th/final page (titled "4 YOUR INFORMATION), hit the "See Rate Terms" button and you should have something expanded like below. From there, you can see if your new times will meet the requirements. If not, the rental will be repriced at return into something nobody will be able to advise in advance).