I've never needed to spend much money or time on this. If it's a vehicle that I receive in this condition then it may need some wet-dry sanding first, but otherwise or after that, just 3 minutes with plastic polish once a year, or two to three times a year if it sits out facing the sun. There's no way it is cost effective to me to apply a UV sealant (that you then have to eventually strip all the way off once it degrades), and buying new assemblies instead is about 20X the work, and you STILL have to either replace them again or polish them every so often.
Heck, once you get them restored the first time, you could even take a piece of cloth and toothpaste for a minute every time you wash and that will be enough. Besides you want to get all that bug and road tar off anyway when you wash.
I get it though, people like to feel that if they choose the most elaborate and expensive way to do something, that it must be better. Yeah you can spend 10X as much money and time to get a 5% better result, which makes less difference than how often you wash the road grime off, which again is a time you could have just used the toothpaste to polish while it cleans.