I agree, a 400-500 mile day is about all I care to do. I often vacation in Taos NM and drive there from Austin, TX. I once did the whole 800 miles in one stretch but today I prefer to break it up into two days. It’s way less stressful and I consider the road trip as a part of the vacation.
Now these guys are the real pros, or lunatics, I can’t figure out which.