I though they only go yellow because of the harsh sunlight in Japan, we don't have much to worry about here. I checked the FAQs before I bought the kit
"Does 3M offer a UV coating with the kit?
No, we have found coatings can have several limitations and negative effects on the headlight
lenses. In many cases the coating does not bond well to the lens and begins peeling or chipping
off after a only few months. The coatings can haze the lens or mask the final clarity of the lens.
Many of the coating will actually degrade under UV faster than the polycarbonate lens material