As stated you can drive about 200 miles with no change. But as you move away from the spot beam the signal gets weaker and soon no reception. So you call DTV (it is not automatic) and they program your service address to a new spot beam. All receivers are updated including your home receivers and they are now out of range of new service address and bingo no local signal for them.
I've never seen a post that locals will work for 1200 miles. If that is at all possible based on my experience it would require very large and high gain dishes on both ends of the spot beam. Much larger than your current dishes. But I don't travel on the east coast so perhaps others will chime in.