my 2cents is that windshield insurance is always worth it. In AK it only raises my rates by about a buck or two every 6 months and I get a new windshield whenever I want. I am going on month 5 with my limited and I have maybe 2 small chips in my windshield already. We don't use salt here either. Downtown they use some salt compound spray solution, but not as corrosive as salt. On the rest of the roads it is sand. So far, nothing as bad as our truck gets dinged, but I think that is mostly due to the angle of the glass then the type.
Hope that helps.