Ok folks, this one is for, well, everyone who often parks outside.
Basically all newer vehicles have plastic lenses on their headlights. There is good and bad to that; the old "sealed beams" were glass, which meant a thrown rock could break them (and often did.) Plastic is a lot more resistant to that, and offers (for those without LED lamps) replaceable bulbs.
But -- plastic is subject to severe UV damage. So is your paint, but that's a different story.
So you see all manner of cars running around with headlights that look more like reverse lamps; you can't see the bulb when they're off, and when they're on they don't throw light worth crap since they have a nasty diffuser in front of them. In states with mechanical inspections these will fail you, and in ones without they might cause you to get into an accident at night because you can't see a damned thing.
There are myriad products out there sold to remedy this. Some even claim to be able to prevent (or slow) it happening again. On that latter claim: Bull****. It will happen again for the same reason it happened the first time -- it's that big orange ball and the UV it emits and manages to get down here to the surface.
So why not just go to the auto parts store (or aisle at Wally or wherever) and buy one of those, and use it, or pay some place to do it for you?
Because they're ripping you off, that's why.
Let me introduce you to a set of products that I have kept around as a pinball collector for a long time to take care of scratches and discoloration of the plastic parts on pinball machines -- Novus. Their "7100" plastic polish kit is what you want and it costs about $20 for the 8oz (per bottle) size. Ignore the cloths that are in the package and go buy a pack of heavy terry-cloth shop rags; $10 or less pretty-much anywhere, typically for 10 or 20 washcloth-sized cotton ones with a nice, heavy and coarse weave. If you have an old washcloth you don't care about that'll work too. Don't get fancy with the cloths; "microfiber" and similar will actually do a worse job.
The Novus package has #1-3 in it. #1 is a cleaner and comes in a spray bottle. Ignore it for this purpose. It has a purpose, incidentally -- the interior clear plastic over your instrument cluster, and there you DO use a microfiber cloth and a very, very light touch. That acrylic scratches very easily and when the sun hits it at the right angle after that happens you'll see it and its very, very hard to completely get rid of that too. But I digress.....
If your headlights can easily be removed do so; this stuff will destroy paint (the clearcoat) very rapidly if you accidentally polish the paint with it. On many GM trucks its either two bolts or, in the case of many Suburbans, two "pins" that require no tools. Unplug the actual light bulb wires and remove the housing. Now you can't screw your paint job. If it's hard to get the housings out (in many cases you have to remove a bumper cover or similar to get to the bolts) then use blue painter's masking tape to make sure you don't screw up.
Put a dollop of #3 ("heavy scratch remover") on a corner of the towel. You want a small area here, not a large one. Using finger pressure concentrated in that small area where you applied the compound firmly polish in a circle. Not lightly -- firmly. Add more compound as necessary and do the entire headlamp. Then wipe it off with a clean section of the towel. You'll have wildly-noticeable improvement.
Now use #2 and do the same thing.
Even badly sun-damaged headlights will be restored to nearly new visibility this way and it only takes about 10-15 minutes a headlamp. The best part of it is that there's enough in those bottles to do a crap-ton of cars -- or yours, a bunch more times. $20 is roughly one or two of the kits from various vendors depending on who you buy them from and trust me when I tell you that in nearly all cases they don't do nearly this good of a job. Beware the kits that include ultra-fine-grit sponges in them; while you can use those for wet sanding as the first step it's pretty-easy to screw things up if you're not used to that sort of process.
Warning: Do not use a power buffer or any sort of buffing tool in a drill for this unless you have a lot of practice with using one on plastics. It is very, very easy to overheat the plastic with the use of power tools and if you do you'll severely damage or destroy the front lens, forcing the purchase of a replacement. Yes, it's faster but has a LOT of risk unless you do this sort of thing all the time, and if the headlamps are in the car it's a lot easier to wind up damaging your paint by skipping off the lens of the headlamp too. It's nearly impossible to overdo it and trash the lens with your fingers. Use your fingers and remember -- firm pressure and small circular motion -- it does not take long at all when done by hand.
Now you can see at night and, if in an inspection state, you'll pass -- and when the lenses inevitably get a bit cloudy again you can repeat the process and, since its easy and you already have the polish you'll be motivated to do it at the first visible sign of deterioration. The cloth you used can be laundered if you'd like; the polish will come out in the washer and thus you can re-use it.
Give the bird to the rip-off artists who love to sell "our special snake oil."