I have the same vehicle (year and model) and am having the same problem. I'm on my 2nd battery and it is doing this again, except mine seems to go for over a year and a half before draining down. One thing after another starts messing up. The remote start quits working (service dept said this would fail when battery starts dropping). Sometimes the reset driver seat and mirror positions fail. So I figure it's just a matter of time before I get a 3rd battery. Service dept. told me they would have to time consumingly check 28 different things to try to track it down.
So, if anyone knows about this, I'm interested in the answer too.