Only the regular G2 uses Lexan and it "can" melt if left turned on with a P61 turned face down accidentally. All other Surefire lenses are Pyrex to my knowledge.
AR15, you can tell the police store to send in the Scorpion to SL and they'll replace the lens. You can also ask to buy the Scorpion off of them for a cheap price /ubbthreads/images/graemlins/smile.gif
I've managed to "bubble"/warp two of the standard Lexan lenses with use of P61s after EXTENDED runs.
While the Pyrex will prevent this from happening, you've gotta remember that it's a trade off for more thermal protection against shock/chip resistance with the Lexan.
/ubbthreads/images/graemlins/smile.gif
Balance these two factors out, and you'll be Good-to-Go.