The rule is you need to return the receiver(s), multiswitch(es), and LNB(s) when you cancel. If there's valid reasons why you can't, you simply call them and explain it. I've yet to hear from someone who was still forced to return it or got charged after explaining things.
When I cancelled a couple of years ago and the rep told me about returning the LNB, I was actually surprised, thinking they only wanted the receiver. He asked me if it was up on my roof or somewhere that I couldn't reach and if so, they'd waive it. I told him it was pole-mounted and it wouldn't be a problem. A co-worker's dish was mounted on his single-story garage roof, at the eave, so it's barely 10' up. He told them he's afraid of heights (really is) and couldn't get it. He had no trouble either.