I got 29+ hours of good light before I got bored with the test...when I say good, it was about equal with or slightly better than Opalec bright. And I used mediocre alks. I love this light.
At 2 hours, it was basically still as bright as a fresh BB 400 or LI.
It is now my "go to" light for anything, but especially outdoors, when a big light is not needed or when I want to save my BB.