Wow! That's simply amazing!
My previous record holder was the BLF AA-Y4E, which also managed a bit over 60 hours. The Ultrafire C3 SS from Manafont also receives honourable mention for more than 48 hours of surprisingly bright output on low. But the UF-H2 now has handily beat them both. I'm thrilled.
40 hours for the 18650 version. I suspect it'll be running for a long time.
Can't believe your'e really doing it. :D
7 days perhaps?
Well, the cell wasn't fully charged to start with. If I have got it pretty much as low as it goes, it ought to be good for around a week. Now at 47.5 hours. But the reason I put in a part-used cell was to shorten the time. If my estimate of usage is correct it should still be around 4 days.
What it is illuminating is a 450MHz SPARC III CPU wrapped in anti-static bubble wrap.
Ok, my UF-H2 finally gave up the fight somewhere between 80 and 84 hours after being switched on! That's more than 3½ days on an Eneloop!
Now it's finally free for me to test on high power at night... Impressive. Easily lights up an entire large room when pointed at the ceiling. And despite being so small it hardly gets warm.
Need I say that I REALLY like this light?
It is dim at 77 hours, but still going. The cell had at least 650mAh out of it before I started. Time to check voltage and current draw. 3.325V and it won't turn on again which is fine by me as that's an unprotected cell.
Well, you might be interested to know that with a regular Rayovac alkaline AA that's been in storage for several years, my UF-H2 has been running on the lowest level now for 96 hours (4 days) straight and with hardly any noticeable change in output! This would definitely be my headlight of choice for being trapped in a mine, for example. Or for getting through a long dark night around here during a long power outage...
Still the cell was almost depleted with Don's test. If a good full 2600mAh starts the runtime on low i bet the cell dies out of boredom in a good week. However for single AA that is awesome.
I can only imagine how long an 18650 could run on low. But in my case, the alkaline has lasted a full day longer than the Eneloop, and still going. I believe Don mentioned that this has something to do with the lower amount of current draw that favors an alkaline. On high the Eneloop would probably outlast the alkaline.
I had a similar experience. Low current draw greatly favors good quality alkies. for low drain devices alkies are best.
The best application for eneloops i would guess are compact cameras.
Ok, the Rayovac alkaline finally died... after more than 116 hours, almost 5 days!
WOW! That's amazing!
And again, it was not a new, expensive alkaline. Just a Rayovac bargain battery, at least two years old in storage if not more.
A newly charged eneloop would probably last a week or more. 
Bit less actually. ;-) Mine lasted almost 3½ days on a fresh Eneloop.
Hi:
Any of you have changed the switch button cover for a GITD silicone one? Is it possible?
Mine's on the way home, I'll use it at work (mechanics) and I'll like to put a fluorescent button, as I really found it very useful when you stick the light to somewhere and don't want forget to pick up the light when the work's done. Not for the glow, but for the shouty lime green colour wich is very high visual catchable...
Actually i've got an Ultrafire C3 with a custom made magnetic clip and the GITD button works like a charm for this porpouse.
Sorry for my bad english,
Cheers!
Hmmm, glow-in-the-dark switch boot- that would be a very nice addition to this light. It looks like it should be easy to remove the switch, it has exposed screws. But I'm not sure.
I'll try when mines get here. Ordered it two days ago, so long wait still ahead.
Thanks anyway ;)
Just to aswer my own question on the above post;
I received my UF-H2B yesterday. The switch cover is a bit smalller than the regular 14mm(didn't measured it yet, but it's like 12mm), so I can't put the typical DX GITD tailcap boot.
Anyway, the flashlight is wonderful, really really pleased with this purchase. It works with both, AA and 14500.
Cheers