I'm not sure what the Dish Network range is on local channels but back when we had DTV it was published at 250 miles.
This was not true in the past and is still not true today. As mentioned above the spot beams vary in size and shape depending upon location and the size of a particular market. It also depends upon your location. If you happen to be at the top of a spot beam, driving N could cause signal loss in 50 miles but driving S you might be able to go 300-500 miles without loss. Moving E and W will get you out of a spot beam faster (in most cases) than moving N and S due to the oval pattern of most beams. This is true of both providers.