five weeks is a fairly short time for the battery to die. you've either got some kind of abnormal draw or a weak battery.
but yes, disconnecting the negative terminal would prevent that (if the battery's not defective). it will also clear any adaptive values from your ECM and/or TCM, though, as well as stuff like radio presets. on a select few cars, it could cause a bigger issue. new beetles come to mind- i can't remember the specifics, but i've seen them require a trip to the dealer after a battery disconnect. that's really rare, though.