Outback_VT

I have 2000 miles on a 2005 Legacy Outback. I live on a dirt rd, Vermont has snowy and icey winters. I was getting a shake in the car that I was fairly sure was snow or mud build up in the wheels. I rinsed it at a car wash and it was still there. My dealer worked on it and cleaned out all of the mud on the wheels by removing the wheels and also re-balanced the wheels. Is this a recurring problem (ie.e am I going to have to remove my tires and re-balance every 2000 miles in the winter? Any solutions (washing the car every day is a bit tough in -20F weather) Is there a better rim that this won't happen with? The dealer service did say that they have been getting a lot of cars in with this problem and it is usually folks that drive on dirt rds.