About how long does the Impala body last (as in rust wise)

We keep our's outside (no garage space left due to a mint condition 85' celebirty, and a 69' camaro) on a brick driveway. It might sit there for a while without being driven (i can drive in about 9 months)

But we live in Pittsburgh PA, so we get alot of snow, and there is salt on the road's.

So, If I wash it once a week, etc, about how long will it last? Usually the engine last's longer than the car, but people get rid of a car, because the body is shot.