I am old and getting more so each day. At my most recent visit my Doctor, a patient man who takes time to talk with you, said becoming sedentary is a death sentence. It takes very few days in bed for muscles to atrophy, for lungs to congest. The trick is to keep moving and RVing does encourage that.
We do not do long distance hikes, but a mile or two every day brightens our day and make tomorrow's walk possible. Being home is dangerous for me, too much food and too much entertaining. We do a lot better with respect to calories when we're traveling. Every time we come home we manage to gain weight over the summer thought the trend is down.
Arthritis is tough. I can feel it in my hands, a tightness every morning. As well every youthful injury makes it's prescence known as one ages. My practical doctor says getting stronger helps the joints, helping to support weakened structures.
There's no escaping age, there is a learning to live with it.
One of our family's mantras is "Life is a series of choice". We haven't always made good choices but we try to be awwre that we need to make choices and simply not respond to every urge. I will say one of our best choices ever was RVing to the end of our days.