Cree XM-L T6 700LM 3-Mode Cool Headlamp / Bike Light - (4 x 18650)

http://dx.com/p/cree-xm-l-t6-700lm-3-mode-cool-white-light-headlamp-bike-bicycle-light-green-4-x-18650-146501

Has anyone reviewed this light? Looks like 2 amp high and 1 amp low. Even with 12 amp hour battery pack, likely still only 2 hours on high and 4 on low. Are there any good DX drivers? Or are they all inefficient, poor runtime? Fenix would have this lamp running for day’s with useful output, and 860 lumens for 4 hours/ 16 hours 360 lumens.

I mean 4 18650 is 3.7 volt x 3.4 amp hr = 12.58 watt hr X 4 = 50 watt hour
At 156 lpw (T6), 340 lumens for 25 hours… Fenix would get closer to this number (though they would use a U2).

Not 4 hours for 500 lumens. Who accepts this efficiency? Or is runtime something better on this light?