In 2005 I fabricated hail guards/deflectors for the house skylights (Texas). The first set of Lexan yellowed very severely at about the 8 year mark. For the second set I used factory treated Lexan with UV protectant. They are still perfect after 12 years. The boat had the original nasty acrylic on the venturi when we purchased it in 2006. Cracked and cloudy. I replaced it with UV treated Lexan with some sort of hardening process of the surfaces (both sides). Still looked new when we sold the boat last year.