I haven't tried a runtime test on it. Various reviews indicate something like 2 hours to 50% and 10-12 hours to below 25%. In EDC usage I usually end up replacing the battery every 6 months or so, more to be sure I have a "fresh" battery in case something would come up. Back when I got this, it was pretty respectable and it still feels like a pretty good balance of light and runtime for me.

-Eric