We drove, (my son and me when he was going to a collage), from Miami to Omaha Nebraska in 27 hours! We took turns driving, and only stopping for fuel, eating and bathroom breaks were done while fueling, and you had better be ready to roll when the truck was filled! and we actually stopped for 5 hours at a motel, (from midnight to 5 AM)! But that was not an enjoyable trip!!!Yes you want to maximize your time at your destination, but at least to me getting there is half the fun! The 50 MPH average as suggested is a good working figure! Remember Breakfast, lunch, & dinner, fuel stops, and breaks should be included! You do not want a family mutiny on the way! On a "good" day 8 - 10 hours is a LOOONG day! that equates to 400 - 500 miles per day, ( as someone stated 5 days out, 5 days back is what you should plan on. You can get tired the family as well, be realistic in your goals and you will have more fun, which is what this whole thing should be about!!!!