jackal

Actually, I believe the early return penalty only kicks in if you return before your rental agreement expires. The early-return penalty is to discourage you from telling Thrifty you'll keep the car for three weeks, have Thrifty factor that into their availability calculations, and then only keep it for two days and leave a car unprofitably sitting on their lot. If you notify them in advance (i.e. at the time of rental) that you'll be returning it early, that gives them a chance to recalculate availability and take an additional reservation (not literally to take one extra reservation--they can't plan it that closely--but the collective spread of 20 or 30 other people doing the same thing would make a difference in rate and availability calculation). So by notifying them at the time of rental, you should avoid the early-return fee (if it is still being charged), and I doubt they'll recalculate the rate on you (the rental computer system is not tied directly into the reservation system, so date changes shouldn't force rate changes).

However, I can't verify any of this information personally...