I've never dealt with Hertz, but I'm not sure what exactly is unpredictable about Thrifty's hours policy. I see multiple customers daily get ticked off at Enterprise, which has supposedly excellent service and wins all kinds of J.D. Power and Associates awards, because they close at 11pm (several hours earlier than the rest of the competition). The Enterprise guys are literally like, "Oops! It's 11pm! I'm gone!" even if they see customers walking down the hall in their direction. The same thing happens at Avis (which supposedly "tries harder,") Budget (which...er, no slogan comes to mind), and Alamo National--even though everyone else closes later (1:30-2:30am), if I'm in the lobby after that, there are invariably a couple latecomers who ask me, "Is such-and-such open?" When I tell them that no, they closed at such-and-such a time, they get incensed.

Every company ends the day with anywhere from 10-25% no-shows, and none of them stays open for late people who very likely won't ever show up anyway. So I'm not sure what's different about Thrifty. (And actually, the T&C for Thrifty in OGG state that they will actually stay open for up to one hour past closing for confirmed reservations with flight information entered for flights that are delayed, so they go above and beyond most other companies and locations!)

A tip for next time: if you call the location directly (as opposed to the 800-number, or at least have the 800-number transfer you) before your flight takes off (after you know it will be delayed--most delays happen on the ground before takeoff, not in the air) and ask the shift lead or manager on duty if they can stay open a few extra minutes because your flight will be late, most of the time, you'll get an answer in the positive (it's a lot harder to say no to someone directly!).