If you decide to go with a cleaning service be sure to ask exactly how they do it. We were considering having it done to our stick house shortly after we built it. When we talked to one of the services part of their process was to spray some adhesive type spray into the ducts after cleaning. Their reasoning was that it would keep dust down in the future. Needless to say if this procedure were to be applied in the motorhome ducts sometime in the future you could have a nice collection of stink bugs glued to the inside of the ducts. Probably not a good plan.