Like a previous poster said, I held a CDL for many years and used it only in an emergency when we needed a delivery and had no other drivers available. Retired at the end of 2011 and kept it until renewal time. Then I made an economic decision. The CDL renewal for four years was over $90 and downgrading to a non-commercial class A license was just over $40 for four years.
Since I've turned down numerous opportunities since retirement to "just take a load here or there for me" from truck operators, I was pretty sure I had no need to keep a CDL and was comfortable downgrading.
As for the possibility of states requiring medical exams for RV drivers somewhere in the future, it could happen, but I don't see any need to worry about it today. Since I have regular visits with my Dr. it would just be something to have taken care of as needed.