On long trips in the motorhome, I usually drive 12 - 14 hours, roughly 800 miles. Nine hundred miles is the most I've done in the motorhome. When we had a travel trailer, I didn't like driving more than 10 hours, although I did drive 14 hours on one occasion as we were crunched for time.
The bulk of our camping is within 5 hours of home, so that's an easy trip. Our seasonal trip in NJ is about 800 miles and we generally do that in one day. Occasionally, we'll stop in MD so we don't get to the campground around midnight. Although now that we are paying for the entire season, we'll probably drive straight through.
-Michael