blinkycat, I ran an earlier test with freshly charged 2000 mAH nimhs, and the light only went about 1 hr 50 minutes to half power. However, when I tested the voltage of the nimhs coming out of the light, one was basically at zero and had in fact failed completely, so the light was not running on two healthy, charged battgeries. When I swapped that one out again and ran it again, I got 3 hrs 25 min to half power.
It's a pain to run these tests over, but if you check your batteries and get a good pair, there's a good chance you'll get more time out of it.