Geocritter,
Yes Sir, this topic's been around, on and off, for quite a while and, it's always a presidential debate. The long and short of it, some guys NEVER climb on their roof and never see the condition of it, some don't think anything has to be done to it, EVER! Some, do a yearly wash and that's it. Some, do more like wash, protect with many forms of products.
Long story short, our previous coach, a '99 Fleetwood Bounder 34V, had a deteriorating rubber roof, the EDPM version. Well, after about 6 years of ownership, and sitting directly in the hot, So CAL sun, that roof was almost completely BLACK, due to the fact that the white coating was just wearing away.
Well, after quite a bit of research, I finally decided on the Dicor product. It's a two part process. Here's the scoop. It was all done in one day!
1. Wash with good soap and water and good brush, let dry.
2. Apply "primer/prep" and scrub, then, "PRESSURE WASH OFF"!!!
3. After that's dry, apply first coat of new coating, let dry
4. Apply second coat of coating.
Now, that was about 5+ years ago an it looks as good today as it did the day we did it. No more black, no more streaks and, considerably cooler inside the coach due to a white roof, not solar black one. Now, that was way back then, there certainly could be more economical coatings out today.
Scott