I got a couple of these to use as a helmet/beam light but to be honest it was a bit weedy and didn't show up against even the peripheral throw of my main bar light.
So...I upgraded the LED for a 240 lumen Cree XR-E from here:
Delivered via TNT 2 days after ordering - parcel said it originated from Bucharest!
Needed to clip a tiny bit off the corners as the star is a slightly different shape to the old one, then 5 mins to de-solder old and solder in with the new. Just unscrew the lens housing and it's two wires on the front surface and the star is not bonded in or anything - couldn't be easier
I don't know if it gets the full 240 lumens now but it's significantly brighter than it was before. Should be pretty good as a helmet beam light once I figure out the best way to mount it.
I also tried one with a seoul p4 LED but it wouldn't fit into the lens without widening the base of the reflector cone. Either this, or the 120 degree viewing angle of the LED has totally ruins the focus of the beam and results in a ring with a dark spot in the middle and is far less bright than the Cree.
No idea how long the batteries will last, but I have an extra battery holder from the P4 experiment to take loaded up as a fast swap spare.