The family and I just returned from our 3,000 mile trip out west. Yellowstone seemed to be the only campground that was full along the way. Other than there the rest all seemed to have availability. The DW and I decided 400 miles a day should be the max from now on for a relaxing day of driving. We did 500 miles a couple times and seemed to be rushing to get all set up and eat before dark. I averaged 65mph on the flats but in the mountains I added a couple hours in for cushion. Never know what speed you will do or what can happen.