longest lasting aa flashlight candidates

I was just wondering what would be the longest lasting flashlight on aa's the eternalight is the longest I know of what would be some of the other competitors.

UK eLED (4AA): 0 to 12 hours regulated, 80 hours total.

Xtreme Light Dive Light, 32 hours on low.

Staying on continuously?

For AA type light, I like the Lightwave Pro 2000 (Flood type, 3xAA w/ 4 Nichia LEDs).
It has enough light to do many tasks and is "rated" for 300h runtime on the package. I think their low light rating threshold is pretty low though. I use mine a lot and the batteries seem to last a very long time.
I use the 3 C cell version when I need more work light.

The old CMG Infinity (not ultra) task light was rated for 40 hours on one AA. Not that bright, but tough, very long run time, and can still be found on sale for as low as $10.

I think the green LED version was brightest and I still use mine a lot. Has that good old Infinity front twisty design, too.

Do you just mean AA format?
There are single led lights running on these weird lithium tionyl chloride AA cells that'll stay on for more than a week continuously with almost no dimming...

Take a look at some of the runtime plot stickies in the Reviews Forum.

Do you mean useable light, or enough to power up the LED? I have a Nerdnik mod drop-in that's been going non-stop for about 3 weeks now. It's dimmer now, but enogh to walk around the house with dark-adapted eyes (2-3am).

A 50uA (0.05mA) or so drive current is enough for a "find-me-in-the-dark" use; sub-mA drive current will already give you enough light to read a watch face and do minor tasks at night; when you go to 3-5mA, you can basically walk around with it; things go progressively brighter up to ~20mA, then the brightness increase is far less notable and the efficiency drops quickly. So, you should really define what do you want to do first in order to get the proper recommendations.

I mean a led torch that puts out enough light to walk in the bush, or around the house at night.

LEDcorp's Turtlelight also sold by Dorcy (41-2498) nexXtech and others.
LED museum reviewed them under both Turtleligght 1 and Dorcy Cool Blue #1.
Dorcy claims 200 hours on the package! Ha!!!
I got 24 hours on 1500mah NiMH before one of the batteries dropped to .5 volts and I aborted the test. The other 3 was still measuring 1.2 volts. My estimate for running disposable alkalines into the ground is 50-60 hours usable light with the rest in moon mode.

The bulb is a standard PR2 base type so you can use it in any torch that takes a 6V PR2 bulb. I use it in Dorcy's focussing latern to gve both area and spotlight by sliding the focussing knob. Dorcy has a dedicated LED version of this on their website. See review here
http://www.flashlightreviews.com/reviews/dorcy_ledlantern.htm
The LED version does not seem to have the circular groove on top of the dome of the incan units that make a mess of the spotlight beam.

You can also try a TerraLUX TLE10 microstar1 on a 2AA minimag. 20 lumens 18 hours. Mine is waiting at the post office so cannot comment at this time.
[EDIT]
Forget the microstar. I got mine yesterday. Horrible beam. Nice white round hotspot surrounded by unacceptable yellow corona

several things make for a long running AA led light.
1-current draw of the LED(s)
2-efficiency of the LED(s)
3-regulation circuitry can extend useful light output
4-more batteries increase available energy capacity.
5-a seeing eye dog that can see a dimmer LED than you can
6-optics and reflectors may help focus some scatter
7-variable settings may help light output as batteries are depleted.
8-higher capacity batteries/chemistries

probably a few more things, the newer 20k+ LEDs and new nichias and other higher quality LEDs will give more light for less power than oem leds which can be just 8-12kmcd.

If you happen to have a bunch of the Tadiran 14500C AA size 3.6 V Lithium Thionyl Chloride batteries and 26 K LEDs lying around (as I did), you can put them both into one of the 1xAA toy flashlights at the 99 cent store and get a real long running light that is about as bright as an Arc AAA. I think it should run for near 60 hours. Switch on it is pretty crappy, though...

A 3.6 volt cell should run a led for 200+ hours. You get electrically the same light as the Tektite Trek Lithium. See the runtime chart on the LED Museum site for that light.

Could be. My toy light has no resistor so it starts well above 20 mA. Chimo, in his 26K vs Nichia head to head thread, ran a test and got a 50% point of about 60-70 hours. The shorter run time might have been due to LED degradation, less capacity in battery at higher currents, or whatever...

consider Opalec NewBeam

A led headlamp like a Yukon HL for example would last pretty long on 3AAs esp if you use it mostly on the 3 Leds. Most other dedicated 5mm headlamps run on 3AAAs though, but it gives very very good runtime as well...