Hi Eric,
I began cleaning the two headlights about two years ago. They came out looking like new. I used a Rubbing Compound then a Polishing Compound and a cheap buffer. It seems that once they’re renewed, they last a few months, then begin to get filmy again. I have also used Zymol car wax on them in hopes of protecting them, but that seems to make no difference.
Anyway, I have one headlight that is now turning yellow inside, so I believe it’s leaking and needs to be replaced. Perhaps your parts supplier has some idea of the quality of the headlights they carry. I imagine that an Auto Body shop would be ordering them regularly and have some years of experience with them.
If they buy a brand that “comes back”, I reckon they will switch to another brand.
Can you ask them if they have a preference or know of any brands to steer clear of?