So the headlights on my 2007 Prius were turning white and ugly. I researched online and found several cheap/free "solutions" like toothpaste and bug repellant to be worth what you paid for them. Yeah, it kinda worked, but the fade would come back quickly, like in a week or so, and then be worse than before. What to do? I tried one of the very cheapest headlight restoration kits, the one from 3M for all of $15. I detailed how to use it here: How To Fix Your Fogged Headlights - Zero To 60 Times and I've been very happy with the results. It's abut 2 months later, and they are still crystal clear. The increase in visibility distance at night was very impressive. Too long, didn't read: get the 3M kit and take a half hour and your problem is fixed.
I'll have to try that, my headlight lenses are foggy. A friend tried one of those cheap solutions last year and it worked for maybe a month.
Ah, yes, sorry. UV damage to the outside of the headlight, not moisture inside. A_triant, yup. Even 3M recommends buying a separate wax for headlights, which I bought, in order to keep them nice forever. I view the plastics like the paint, where it needs some protectant every now and then to stay nice. I'd love a forever solution, but like paint, I think they're just going to need occasional work. I'll check out that product tho...