The luck of the draw, I guess. I've got a pair of krill lights that still work after maybe ten years of use at Burning Man.

Krill lights are still made:
http://www.kriana.com/pages/howtochoose.html
but you wouldn't want to throw them away.

Tossing cyalumes into caves and ponds seems not to be a 'leave no trace' event. Different strokes for different folks, I guess. You'd think we've got enough trash on the ground without throwing more into the caves.