The biggest reason these lenses do this is the coating thats on them. Here's the fix and you won't regret it. Get yourself a sheet of 1500, 2000, and 3000 grit wet sandpaper. If you have a DA sander even easier, now get a bucket of soapy water, start with the 1500 and give it a very good circular motion sanding, work up to the 3,000 grit, give it some extra time with the 3,000. Now get some fine cut buffing compound and buff them out real well. Unlike the kits you buy or any other method, you won't be having to do this over and over constantly. Hope this helps. This works on any of your plastic lenses that have gone dull and crappy looking.

Keep in mind that when you do this process, it removes whatever UV coating may have been left on the plastic lens, and the plastic will still yellow over time. For longer-lasting results, a UV blocking clear coat is needed. Some of the kits include the clear coat, but the most commonly used ones do not.