Like Steve said, treat it just like paint. Every time I wash my car, or truck, I mist it with Optimum Spray Wax right after the rinse. Not only does it lubricate the microfiber towel as I dry, but it puts down a layer of protection on everything including the headlights. Every time I do a full detail (about 2-3 times a year), I polish and apply a LSP to the headlights as well. I've never had a problem with headlights oxidizing.

Hope that helps.

 

Good question. I have had my 2001 Screw since new. Never garaged and kept outside in the Dallas, TX area year round. I infrequently wash the truck but only by hand using over the counter car wash ( sometimes with a bit of Dawn dishwashing soap added) and well rinsed. I have never put any wax or sealant or polish on the headlights. About 2 years ago they began to yellow slightly and with in the last year have suddenly began to haze and develop a rough exterior surface.

I have always washed my windows at the gas station with the provided sponge/squeege when I filled up. A few years ago I began to sometimes take a swipe over the headlights when I did the windshield. Now that I think about it, I never rinsed the headlights afterwards. I think I will quit doing that. Who knows what solvents are in the gas station window wash bucket? Hope this helps someone. Its to late for me. I now have to get new lights or start polishing.

Then again, maybe its just the effect of 13 years of UV on plastic.
Does anyone have an original f-150 kept outside in the sun that has not yellowed or hazed the headlights?