Yeah, you don't want that exposed to road salt or other gunk. Being from out west, I never had to worry about road salt until moving to the mid west. Salt's so corrosive, so I hate driving my 2 year old car in the winter here, but oh well, it's got a 6 year rust warranty and probably won't be worth much anyway after 6 years, so I continue driving it in the winter. I asked the dealer about rustproofing. He said you don't need it, since they already do it at the factory.
I know people who drive 'winter beater' cars, but is that worth it? Seems to me, the added expense of buying, maintaining, and insuring a 2nd car for use as a winter beater would end up costing more than the relative depreciation on your new car by driving it in the winter and exposing it to salt. Plus throw in the fact that you'd be deprived of the satisfaction and safety of driving the newer/nicer car in the winter. Guess it depends on what kind of car you have and what it's worth.