Wife and I are early 50's and very active. We are not full timers and honestly have no intentions of ever becoming so but we spend a ton of time in our campers. We don't have a set exercise program in place but mix it up with things we love to do. Hiking, biking, canoeing, kayaking, rafting, fishing, swimming etc...
We both are of the mindset of seeing and doing as much as we can while we are still able. R&R is not part of our camping/traveling routine at this point in time. We rest when get back home.
We have an 84lb Irish Setter. I'm fairly certain he caught and swallowed the Energizer Bunny when he was a pup. A 5 mile bike ride is just enough to take the edge off for him. Had a lady recently yell to me while riding past her for the fourth or fifth lap around the campground "You know your just building up his endurance!" Sadly, I think she was right.