We went to a seminar about cleaning roofs and the guy from Dicor roof said washing it and keeping it clean made it last a lot longer. With that he also talked about all the product out there to clean roofs and said that one of the best is Dawn dish soap. I have washed our roof with it and a mop and had great results. Simple and easy, other than getting on the roof itself. I'm sure there are other products that will do just as good, the big thing is to just keep it clean.