This depends. For a service writer in a commercial dealership (diesel repair) I would consider this to be a stable position. There will always be a need for freight and transportation of goods which are your biggest customers. However, I consider an RV shop to rely more heavily on the individual, purchasing luxury coaches for vacation purposes which will be the first thing to go if the economy takes a dive. The best opportunities would be found in larger cities along major interstates where you would expect the most amount of traffic and least amount of potentially dangerous weather.