It's not just for the sun.
CO from car exuast kills your gasket, motor oil in the runoff, sunscreen, bug spray.
Pretty much everything in the world is trying to kill your gaskets from the moment they are made.
Even before they are installed on your top they start to degrade, sorry for the bad news, so the more you 303/silicone NEVER ArmorAll, the longer it will be till I have to replace them for you and don't forget the wrists.
Rinse the gaskets after you use it too.