Installing comcast digital reciever

Hey I got one main reciever and two secondary recievers a few months ago, and hooked them up. Alot of channels were "unavailable" that we previously use to get. Because of this we disconnected them.

Now supposedly two days away from some kind of change over, I am hooking them back up and waiting for the activation to finish as I type this. My question pertain to one of the secondary rooms television.. It doesnt stay on, wich is what the installation asks for. I cant see this causing much of a problem but they specifically say have all tvs on.

It worked before when this one tv was off during installation. But the only problem was the few missing channels... I am wondering if these channels will work once the full change over takes place? I am thinking I should get a few extra channels rather than lose a few?