Question on lifetime of rotomolded polyethylene boats

I keep my thermoform boat locked to my dock in the summer. Bought 16 feet of a Sunbrella type UV protection fabric and use it to cover the kayak as the dock is in full sun in the morning. And 303, the sunscreen for kayaks, on the hull.

Disclaimer: I live above the 45th parallel north near the tip of the mitt, as we call Michigan. We don’t get that many sunny days and the sun isn’t as strong as it is in our southern states. Air temps are cooler as well. But I would never store any boat in full sun without some type of protection.