Looks like you're in Southern Cal. Mildew seems to be an issue, and the fellow next to me was quite upset after getting it a year after new sails.
I don't have much--but once on, it's hard to get off (bleach).
I do hose down and scrub the sails every couple of months, because it is said that dirt is host to mildew, and after a Santa Ana (dusty desert wind) there's plenty of dirt on the boat and roller-furler.