We don't think in terms of miles, instead we use years since most RVs are used about 1/32 the amount of time a car is.
We don't start looking for a new RV until the current one begins to fall apart and becomes too costly and time consuming to enjoy. We had our first RV (a very used one when we bought it) for only two years before it became a money pit. We had a couple of other used RVs and got rid of them due to problems.
Our new purchase RVs- first one was a 24ft TT that we kept for 16 years and replaced it with a 5th wheel that we've had for 20 years. The 5th wheel is still going strong and has lasted through 3 trucks. The first two trucks were used and replaced due to problems. The current truck was purchased new and from the way it's holding up will be around for a long time.
Keep in mind Class A MHs are built using the same suspension and drive components used on commercial fleet vehicles. These parts are designed for a minimum of 500,000 miles of use. They are not like cars or light trucks designed for 200,000 miles of use.
So if you are happy with it and you aren't having problems with it and maintain it properly...why get rid of it.
