I like battery stories.
I had a 2006 Dodge Charger RT OEM low maintenance battery last 7 years. I replaced it only because Summer was approaching. My 2000 Corvette battery lasted 7 years. However, my wife's 2013 Charger RT battery has drained twice in the last 11 months when sitting idle for 4 days.
I'm guessing the latter is a problem of proximity. I theorize the key fob is about 6 feet from the car, and therefore remains in communication with its computer. The car never really goes into sleep mode... I think.