Almost all electronic devices (now) are always on in low current mode checking to see if you have pressed the power on button. So if you put your device away long enough (Never turning it on) the small drain on the battery will discharge it until its dead. So store your batteries outside of the camera. The exceptions to this are devices that have a real switch that disconnects power to the device. Sadly the people designing things are pretty dumb so we have things like phones that are never really "off" unless you take out the battery.