Many years ago, people started giving up the RV lifestyle around 70-75 years old. At that point it became too much work and felt it difficult to handle some rigs.
As we all know, life expectancy has been extended by drugs, awareness and taking better care of yourself. I think the new age for many to evaluate their skills is probably closer to 75-80. There will always be some that drop out sooner and those that surpass the average.
Hopefully, people will listen to their families and friends when the time comes, but giving up the freedom that driving gives you is tough to let go. My mother in law, who had a debilitating right side stroke at 82, was angry at me when I sold her car a year later. She said she was going to drive again no matter what. There was NO WAY she could ever be safe behind the wheel again, but she couldn't see that from her wheel chair.