As a commercial contractor that has used hundreds of thousands of square feet of EPDM roofing rubber I can tell you that we usually guaranty the roof for 20 years and it requires NO maintenance at all. I have also never seen any of the hotels or warehouses, where I have used the EPDM roof, send people up to wash it. :B
To comment on the marketing materials. EPDM roofing is 100% repairable, which contradicts the marketing BS. You can cut out a section and replace it and seal it up as good as if there was a solid piece of roofing. The EPDM roofing materials on a 10' x 50' single roll, white or black, would cost less than $1000 from any roofing supply company.
The RV industry is a very small user of EPDM roofing materials.