When I bought a new house a few years ago, I didn't use Dish Mover because I had a 3-month window where I wanted service active at both houses, so I just opened up a new account. When I finally cancelled service at my old house, they asked me to not only return the receivers but also to take down the dish and lnb and return them as well. When I told them that the roof was too high and dangerous for me to attempt to remove it, they told me to forget about it. My old house is now rented out (cuz of the poor sellers market), and the tenants are using Comcast instead of Dish. The dish still sits on top of the roof to this day.
I guess the point of my story is that when push comes to shove, Dish isn't going to care about the extra LNB that isn't even being used or is assigned to your account.