What I don't really see here is "hours" per day, only "miles" per day. THAT is what you need to figure out.
Some years back, while we were still young, we drove straight through from SoCal to Eugene, Oregon in a 23' class C. Switched out drivers each fuel stop (one slept while the other drove), prepared/ate meals while on the move, only stops were for fuel; nothing else. 1,000 miles, 17.5 hours. It averaged out to about 57 miles per hour. 60-65mph over the long haul is just not reasonable in an RV; just fuel stops alone will drop that number significantly. If you are going to stop to eat, or even to just stretch your legs occasionally, then figure on 50.
So while 500 miles is just over 7.5 hours at 65mph, at a much more realistic 50-55mph average it is 9-10 hours. Are YOU comfortable being behind the wheel for 10 hours? If you are, then more power to you; I'm not.
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