I spoke with Gem Services in Ventura(Detroit Dealer) regarding the rockers and cams. He confirmed the RV Engines need to be run more often, once a month, 15 miles or so. Also, Dave said some scratching is tolerable. No special oils or treatment will avert or help.
He also recommended having it looked at at 100,000 miles. According to them, if you hear something, it's probably too late .