I responded to a similar post on the forum. Here's my reply:
https://www.1addicts.com/forums/show...23&postcount=2
The DIY kit I used was cheap and super easy. You may want to consider trying it out. The results were great. Many months later, the lens of my mom's Jeep are still decent but seems to be not as clear as when I first did the job. But frankly I haven't been closely staring at the lenses when I'm around her car. I'll do it next time if I remember to see if and how bad any hazing/dulling there may be.
But the members that say to use PPF are spot on. I have PPF on two of my cars. My 1er which is garage kept and sees weekend use and my C-HR that sits outside all the time and is my daily. Both of them are still super clear. I suggest whatever you do to restore the clarity of the headlight lens that you follow up with having PPF put on to prevent any possibility of future hazing again.