I really don't know how much movement it takes to have the dish become misaligned, but it's almost assuredly not much. With a mobile home I can see it happening pretty easily due to adverse weather conditions, or even like you said, just the changes in temperature due to things expanding and contracting.
Is a normal pole installation possible for you or would it not be high enough to clear obstacles? They mounted my original legacy plan dish on a pole they installed, then mounted my Gen4 dish on the same when I upgraded. They did a fantastic job of setting the pole and it has never gone out of alignment in twelve years, even with the wind and snowstorms that we get rolling off of Lake Erie.