I can only speak from my experience. I had my XFire for three years and 26,000 miles. No fogging, no condensation, etc.....however, as soon as I purchased the car I put XPEL on the lights to protect them from rocks, etc., and that may be the reason I never had a problem. I also put the material on the fog lights for the same reason, and had no problems with them either. Here is the address if you want to check it out out.

http://www.xpel.com/