Depends on whether you are in the fringe outskirts of the beam. Then I could see it losing strength. If you are within 100 miles of the beam area you are usually good. At least the Houston spotbeam is the one I use and I'm 90 miles from the city itself.
It depends on the shape of the spotbeam also. Some aren't round but oval. So those me go out 90 one way and 150 another. It is possible for a spot to go down due to the condensation of the air making it harder to penetrate.