Winter Use W123

[rmmagow]

When I first bought my current W123 it was (and is) in such good shape I thought I'd perform a restoration. Ha Ha Ha, like many a plan, I am starting to realize this ain't gonna happen so I want to use my car but not abuse it. To keep rust at bay I will not drive it during snow/ice storms but I will drive it on roads that have been salted and might be slushy enough to build those huge mounds of kicked up garbage in the wheels wells. The car has virtually no rust on it and I'd like to preserve it as well as I can. Am I better off letting the car just sit in a frozen state during the cold months or should I attempt to wash the underside even though it is still winter? I don't hate the car at all and will drive it probably until I can't drive anymore (not too long unfortunately, 10 years, maybe 20) and don't want it to just rust away. I go over the car annually and spot fix any rust issues and have not had any rot issues to deal with and I keep the drains clear. So I guess my basic question is do I try to rinse out the salted crap or will the freezing temps keep it from doing a lot of damage?
Thanks for any and all suggestions for preservation.