Looks like the film doesn't particularly protect against UV, but, of course, does protect the lights from damage and breakdown of the coatings.
Here is the reply from Headlightarmor.com:
"While all the materials do have a UV inhibitor we do recommend regular cleaning and conditioning with a high quality vinyl cleaner, such as 303 Protectant, Mothers Protectant, and Meguiar's Gold Class Vinyl/Rubber
Protectant. We use 303 and Meguiar's here as they are effective and readily available at car parts stores, boaters stores and even some hardware stores.
Come to think of it, it is probably a good idea to use it even if you don't have one of our kits installed...
Plastic / polycarbonate headlights found on most new cars these days can cloud due to a wide variety of factors. UV is one for sure, but most mfg's use a UV/scratch coating to help out some. Other (bigger) factors are micro pitting from sand and road debris. Just as your windshield will develop millions of tiny pits over time, so will unprotected headlights. Chemical burning is also a real problem, especially with car washes (automated, semi-automated w/washaterians (you know the 15 people spraying who knows what on your car...), and even dealer was people.)
While installing a headlight protection kit won't prevent everything it will do a great job against the micro pitting from every day driving and a good job against some errant chemicals (though care should still be taken) and of course regular maintenance of the materials."