Alot of people have brought them back by holding a heatgun on them for a second - never done it myself, but enough people claim it works for me to believe.
Personally, I use forever black - it works perfectly. More of a dye than polish.
x2 on the heat gun. you can even use a hair dryer, just keep an eye on the heat and work it slowly. works good and you wont need to do it again for a long time.
The heat brings the dye up to the surface of the plastic, hense rejuvenating the color. actually works the best of any of the stuff i've try'd. dont have that problem anymore though.(no plastic flares)
I detailed cars for two years while going through college and we always used Armor-All. It keeps the shine long enough for the salesman to get it off the lot. It's not a long-term fix but it looks good for a while.
JK, but I did hear that using Vasoline annually as a "buffing agent" will keep the color longer if they are not yet faded. I have no experience with it myself.
Ya heat gun or a good hair dryer is the way to go!
If you use any type of chemical on them make sure it doesn't have any alcohol or anything in it...which will just cause it to dry out even faster. I know Mcguire's and Mothers both make a good plastic and vinyl cleaner/protector that I've had pretty good luck with.