This is becoming a consideration for me lately, but my solution may be different than those who live in climates that get more moisture than mine. We get snow and the cold, but we also only get 12 inches of total precipitation, which is mostly snow. While this year has been the longest I have gone without driving the ///M, it only rested for 4 weeks maximum before I was able to get it out to play a bit in dry sunny, but cold weather.
We do not use salt on the roads around here so I don't worry about rust too much. I just wonder if any of you have considered just driving the car when the roads are clear of snow and ice.
'00 MRoadster, '00 528 now in other hands, '07X3si, '14 535d XDrive