The specs. for the 3 watter is roughly around 1 1/2 hrs. before dropping to 50% I believe but what happens to the run-time when you add in an extender to run off of 3x123's? How much longer is the run time?
Flashlightreviews.com says output is at 50% at 2 hrs. I have used this module in a 9P with great results, guess (FWIW) would be approx. 3 hrs. (1.5 x time with 2 cells). What I do remember is that the light seems to run a lot longer than it *should* on 3 primary cells.