GMC Repair: 2006 GMC Envoy Denali battery dying?, gmc envoy denali, jumper cables

Question
We have a 2006 GMC Envoy Denali that gets drives maybe once a week, if not longer.  Several times the battery has been dead and my husband has had to use jumper cables to get it to start again.  A few months ago we took it to a GMC dealership to have a repair done and told them about this, and they couldn't find anything wrong.  The only suggestion they could give is that our car has an aftermarket car alarm, and that was the only thing they could think was draining the battery.  Any ideas?  Thanks

Answer
is the car alarm still in the vehicle?  If so it would be the first thing I would remove, after that you could check to see if the onstar module is staying on or the xm radio module if it is equipped.  Other than that it could take a bit of time and expertise to determine what is causing the draw