I haven't found a good headlight restorer that lasts.
It seems once you sand/polish the top layer off it removes any UV coating that is left and the plastic just fades quicker and quicker after the first restore. QUOTE]
I have polished a half dozen plastic headlights and all have turned yellow again within a year or less.
Once the protective UV coating has been removed, the game is over. Many times, you can see the remnants of the original coating being removed, while polishing.
None of the kits come with an effective coating, the best just put a temporary coating that looks nice...for a few days, before evaporating.
Once your headlights start hazing or turning yellow, start looking for new headlights.
I sold a nice, older Acura last year because the HID headlights had become unusable and new housings were $700 a pair, if at all available.
What XJ has plastic headlights? Stock XJs are glass. Even the aftermarket E-code housings are glass.