I was told 7 years depending on weather and etc (probably shorter for you since it's going to be outside most of the time) from my local wrap guy who did mine and assuming you're going to use good qulity vinyl. As for cleaning he told me to use Plexus. It cleans and gives a nice glossy shine to it. But I'm sure you can gently clean your roof with a soft towel or something.
Mod clean my friends.