Okay, so after 30 hours, the K2 is not quite as bright as my photon-type keychain light. At 36 hours it was still usable, but you wouldn't want to read a book with it, and forget about anything out past 10 feet. So at 40 I gotta think those batteries are gone, and all you will get is a glow much like an ember.

I've starting thumbing through the survival book, so far the front end is all about animal and plant recognition and nice to know stuff. Down deeper it will get into the DIY stuff like snares and traps and signalling and how to make fire etc.