Remove the coax from the satellite in on the back of each DVR before you call, however you probably won't be able to watch recorded programs the entire 6 months only a short time (which as I have read from other posts can be anywhere from days, weeks or [unlikely] months).... YMMV. Also I believe if the DVR loses power/reboots you won't be able to no longer watch either (might be a good idea to have a UPS).
Your mileage may vary - perhaps depending on if the DVR was leased or owned. I have an SD DVR for which I canceled service a couple of months ago, removing the coax first. I can still readily access recorded programs today. And we had a power outage just last night (no UPS). I just remembered - it also has no authorization card as D* wanted it back. That seems to have been hit/miss with my owned DVRs. Sometimes they want the card back, sometimes not.
Edited by Tubaman-Z, 21 February 2014 - 11:26 AM.