Buddy, try what Curtis/Ryan suggested, a small percentage will come out good for a long time however if its anything like the AE111s I've worked on, you have to keep repeating the process every 3-4mths depending how agitated you get over the crappy looks. Basically the outer coating on the plastic lens wears off, just like clear coat on your painted panels and it oxidises/fade in the case of paint.

When you do it once or twice, then see if you feel its worth it for a replacement or not =)