I gave my new headlights a couple of coats of CarPro Dlux when I first got them and they are still in brand new condition after nearly 3 years
I also give them a coat of wax anytime the cars getting done
Whatever you do to them DO NOT use anything abrasive, no polishes, compounds or glazes
When they are new they have a protective UV coating on them if you use anything abrasive you'll damage the coating and your headlights will age faster
Also it's the sun that makes them age fast so the more you can keep them out of the sun the better mate
Hope that helps