I have driven solo 850 miles from Garden Grove CA to Albuquerque balloon fiesta twice. Not a lot of fun, and it takes a day to recover. That was in a pickup with a camper, and much easier to drive a long distance than my current class A motorhome. And I was able to drive around 70 back in the $1 per gallon fuel days. I did stop every 4-5 hours for a 2-3 hour nap.
Now I am much more likely to drive less than 400 miles per day, and might streach it a bit to make it to the destination in one day if it is only about 500 miles. But would rather break it up into two days, and not have to spend the next day recovering and sleeping all day.
If you have kids along, plan on a lot of video games or less than 300 miles per day. That is about 6 hours driving and figure you average about 50 MPH while driving 60, to take into account fuel stops, and restrooms.
Fred.