This may seem sacrilegious, but I generally go through winter without washing. On the last reasonably warm day of fall, I'll lay on a coat of
Collinite #845 and just let it go until spring. It really seems pointless to keep washing throughout winter, as the car would just get re-salted almost immediately. The wife insists on running hers through an automated wash regularly all winter, and it usually stays clean for less than a day.