DW and I are both 75. Just got back to home base from a 3,500 mile round trip. Outbound was a lot of short days 50 to 150 miles. We trade off at the wheel every two hours so no one gets tired or strained. The return was different. DW needed to get back to doctors and was advised not to drive. I did 4 days of average 350 miles with stops every couple of hours to rest the butt and empty the personal holding tank. I am surprised and happy that I was able to handle all the driving without feeling any stress. We try to keep speed at or under the low road speed so we are being passed not passing, but not so slow as to impede traffic. My reflexes are those of a 75 year old and I drive to allow for that. Since DW has as many miles at the wheel as I do, she is capable of taking over even "on the fly" should bad stuff happen.