When I drove from Phoenix to San Antonio (14 hours straight) I was surprised that I didn't feel more cramped than I did. I only made 2 stops each way for gas/food. I was comfortable the whole way. I would need to adjust every now and then, but it was never uncomfortable.
Of course, come to find out I had a bald rear tire with the steel belts starting to come undone from showing through so much.
But I guess that's to be expected from putting 3k miles on it in 5 days.