1992 itasca fiber glass roof coatings

I would go to a boat shop and buy enough fiberglass resin to re-coat the thin spots then go over the entire roof with a coating like this. Once your RV gets older, this pretty much becomes an every 2 year or so thing..but hey, still way cheaper than a new motorhome! HD has a more expensive product that would probably be longer lasting and maybe keep you off the roof for 5 years. Depend on how long you intend to keep it!

http://www.homedepot.com/p/Henry-4-75-Gal-587-White-Roof-Coating-HE587871/202091022