Billet mirrors

I asked this in Off-Topic and didn't get much reply, so I'll try here. My birthday present this year (friday) is a set of Billet Specialties mirrors, which is great since my passenger side mirror has been gone for about a month after I went mailbox hunting with it...Anyway, my question is this. Should I remove the billet mirrors during the winter months (we do get some snow and thus salt on the roads) or will they make it through without pitting? The real reason I don't want to have to swap for the winter is that I'm considering mounting the mirrors up the door pillar a little ways and then molding my plate where the stock mirror bolts into the rest of the door, but, of course, I wouldn't be able to do that if I had to deal with mirror-swapping in the winter.