That is a good point and why you should not leave batteries in any flashlight or other device for long term storage. The batteries should always be seperated away from the lights if storing for more then a few days. Besides drain there is also rare instances of leaky or exploding batteries. So the batteries should be stored away from ammo and anything that might easily catch fire such as loose paper preferably in a metal container.
An old military ammo can with a few medium sized holes drilled towards the top for venting and temperature equalization would be ideal. A cheap metal pot might be another idea.
http://www.amazon.com/GI-50-Cal-Ammo...3409045&sr=8-8
Battery explosion is a rare exceptional occurence, but you dont want your house or place of business burning down because of a mis-stored battery.