2008 Tahoe Dead Battery AGAIN

Anyone else having problems with their 2008 Tahoe battery going dead? I have owned this Tahoe since 2007 with no problems. Starting in January 2012, the battery was dead when I went to start the engine. I took the Tahoe to the dealership and to Les Schwab, both said nothing was wrong with my battery. This happened a few more times over the next months. In June, my transmission died (covered under warranty.) A week later, my battery was dead again. After two days at the dealership, they decided the problem was the navigation/stereo/DVD system was continuing to draw on the battery, even with the vehicle off. Nav/stereo/DVD replaced (thank goodness, I purchased the extended warranty!) Over the summer, my battery kept going dead...typically if I opened a door more than two times prior to starting the engine. I have electronic running boards and tailgate.

I only have 60,000 miles and don't feel that a five year old car with such low miles should have this continued problem. The dealership can't seem to find anything wrong with my Tahoe! Any suggestions out there?? I love my Tahoe and would hate to get rid of it, but I need a dependable car!