I also like to have spares... if something goes wrong with one cable for any reason it is an easy plug swap to correct it.
Same reason why I have spare cables run in my internal walls. ( for example between my stereo/av hub and my TV I have 2 x HDMI, 1 x Components, 2 x network, 1 x infrared, 2 x coax). If a new standard comes out (ie 3d required dual HDMI Cables... then I am relatively future proof without a wall teardown).
I think that I am using one currently, but that goes to two soon for MySky. I can go to 3 for a larger dish and more Satellite channels if I want.