Are there any recommendations for protective UV films or any other form of UV protection for the plastic that can be applied once the lenses are clean? Reason I ask is on my LHS, I had cleaned the headlights but they turned yellow again in a fraction of the time it took the first time they changed. I would imagine the plastic is coated with some form of UV protection in the factory during manufacturing. It would make sense whatever compound they apply breaks down over time and as a result, yellow and cracks form.

Any suggestions or opinions on this?