We usually take the 7:45 SW flight, and we always seem to manage to pick a day when the weather in Chicago ends up causing it to come in late. We have arrived after midnight twice now.
For the most part, there are usually only about 15 vehicles left in the Natl. slots, period! Last time, our only full-size choice was a Chevy sedan (definitely a geri car; bench front seat, no cup holders, and the seat belts in the back seat were mounted so far forward of the bight that there is almost no way you could use a carseat with them.) There was also a Dodge Stratus with a smashed passenger rearview mirror, so that was a no-go. The only other vehicles in the lot were large vans and SUV's.
We were told that there is no need to trek back to the counter if there is nothing on the aisle. Just take your pick of whatever is left. We took a 4-dr Blazer, though our carseat was still not as secure in it as I would have liked, and I REALLY don't like vehicles with bad gas mileage. One thing is certain: I can now assure all those folks who tell me that I would love SUV's if only I drove one that they are dead wrong!