I think all manufacturers recommend cleaning the rubber roof. Dicor sure does. I don't know if it will help the owners who keep theirs for only 6 or 7 years, probably not. But if you want to take care of the whole exterior of yours, clean and protect the roof.
I use "protect-all " brand cleaner and treatment. You'll need a good sponge, soft brush, and 2 buckets one with clean water, one to ring out the sponge and brush. Do it in the morning before it gets too hot. Allow it to dry before putting on the treatment--which I just wipe on heavy.
The cleaning removes the sacrificial white colored sludge like material that runs down sides of trailer and leaves black streaks. The treatment is like a clear wax when dry. It is very slippery, like a thick wax, so dirt doesn't stick to the roof easy. Plus it blocks some uv rays from penetrating the rubber roof thus leading to longer life.
Most importantly, you will know every square inch of your roof and can spot areas that need touched up with sealant. I do it and will continue to take the best care of the roof as I can--when the roof fails I think that is the end of a trailer unless it's caught immediately.