I agree with plowing in 4x2 when the plowing is in a flat area with little chance of getting stuck. I do that fairly often.
However I would not stack snow in 2WD and wait to get hung up. Thats a recipe for getting stuck, even after switching to 4WD. When you stack, sometimes you lift some of the weight off the front axle. If you get hung up on a snow pile, chances are your plow is up on a snow bank and no longer weighting-down your front axle.
Whenever you off road or plow snow, you go to 4WD
before theres a chance of getting hung up.