mine cracked back in the summer.. think it was most def some road debri.. not likely heat.. but im just gonna run them.. aint no need IMO to replace them as they come on

 

Have been underwater in mine, too, and have had no issues.

 

Cheaper method to protect the fog lenses...invest in some 3M clear bra material and cover the lenses up. Worked on my PIAA's for the last 6 years and the last 2 years on the JK, no chips, no cracks...when the 3M bra tape gets pitted and ugly looking peel off and replace with new tape.