Don't be too cheap on the collision insurance for a stored car. My friend's son has a '72 corvette that was hit by an SUV that went over a curb through a fence through the garage wall into the side of the vette and then up against a tree. The Stingray looks more like a Wasp now.
Insurance won't cover the damage under comprehensive and the owner of the SUV had marginal insurance. The driver of the SUV (you could perhaps call her a pilot in this circumstance) didn't even have a a valid license. For the $200 I'd save for 4-6 months off of collision, I'd just as well leave it in place.
And yes, I realize the odds for this to happen are astronomical, but I abide by the simple rule that I don't worry about things until they happen to someone I know.
As for taking out the NSX, I usually wait for a dry day in the 40's with little or no snow melt left. In Chicago that is usually June...