Newer cars seem to die after awhile because they always leave something powered. Make sure you have everything off, as if you were parking it for a few weeks again. Remove the under hood bulb to open that circuit. If you have the negative cable disconnected, connect an ammeter (on most multimeters) between the neg cable & neg battery post. This will give you an idea of how much current still travels while the car is static. If there is excessive draw, You might remove fuses one at a time, looking at the meter. You may find a fuse that is common to only a couple circuits, narrowing the problem somewhat. If you let a dead battery sit dead and continously have a load, it prolly will short the battery - start the car regularly or disconnect the battery?