“I have always washed frequently to get rid of salt…” Sounds like your doing fine John. I give it a wash on warm winter days so we don’t end up with doors frozen shut and power windows iced in. Do that and someone in the family will keep punching the the down switch to see if the motor can break it loose. It can’t. Wouldn’t depend on “zero” too much. Salted roads mean liquid. Liquid means salt solution getting into every nook and cranny under the car - which is where I point my winter wash nozzle.