I have Dish not Direct but they're really pretty much all the same.
I used to move my Hopper from home to the coach than I just called Dish and asked for one more Hopper and had it hooked up permanent in the MH on the same account....I called the MH a guest house and the installer didn't care one way or the other.
I'm betting you can do the same thing with Direct with whatever Directs version of the Hopper happens to be. Love HD and he ability to record whatever programs we want. The extra cost of $10.00/month is well worth it.
And, yes, I just call Dish whenever we stop of a period of time and change our service address. However, you may be surprised at just how much coverage you get without losing locals. For example, when we get a Boise, ID local we can still receive them all the way to Anaconda, Mt, Idaho Falls and even well south into NV.