Maybe I am just so used to being out in the bush in the dark that I dont need a light on all the time, but I wouldnt think that you would need more than 12 hours. Are you planning on having it switched on all the time? Or will you use it for short durations, ie looking for something you dropped, or as was stated before, going to the head. Even if you are signalling with it, you wouldnt have it on continuously.

In my PSK I have a princeton tech squeeze light that I got for around five dollars. No constant on mode, but I knid of like that as it will force me to ration my batteries.

Garrett
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On occasion of every accident that befalls you, remember to turn to yourself and inquire what power you have for turning it to use. - Epictetus