WRT leaving a light on and destroying it, there is some truth to that. I've had this happen with three different 'sealed' flashlights. One was my ARC-AAA (old .9 version turquoise), a green Infinity, and my good old 2AA maglight. Go ahead, seal them up, turn them on and leave them for *a few days*. Well past dead batteries (okay, it'll take a week for the infinity). Then try to open them!
What happens is that alkaline batteries generate gas when they are very near fully discharged--the reaction that takes place is prevented if there is much voltage on the cell--even a few hundred mV. Once it's below that, it starts to produce gas--I believe it's hydrogen, but my memory may be off. You can get enough built up so that the pressure pushes on the end cap strongly enough to jam the threads. Fortunately for me, the ARC-AAA had very good silicone grease on the threads and was openable, the 2AA maglight is not sealed between the battery compartment and the head, so just unscrew the head a little to releave the pressure--the threads are of a different variety on the head. The bear was the infinity. It's well sealed and I had some crappy grease on the threads. Also, the head's got enough surface area that the pressure was exerting a lot of force on it (more area to act on). When it finally came off, the head shot out like a bullet and there was a loud 'bang'. The AA cell, once extracted, was making hissing and popping noises for a few minutes. Nasty.
So, be very careful with really dead cells.
