I'm wondering what type of 'regulation' the River Rock 2aaa has. Simple voltage boost, or current regulation? I did an 'eyeball' runtime last night on mine. Using an Energizer 850mAh Nimh I got 9 hours before it dropped into Moon Mode. After reading several posts, I understand it to put out about 10 lumens. Comparing it my Dorcy 1aaa also running on a freshly charged Energizer 850mAh Nimh - which I assume puts out approximately 3 lumen, obviously the RR2aaa puts out more overall and throws about 2x as far (?) After 9 hours, just before it dropped into Moon Mode, it was obviously not as bright as originally, but still out-threw the Dorcy & put out at least as bright of side-spill - so it had decreased to no lower than 30% of original (3 lumen Dorcy/10 lumen RR). Shortly after 9 hours continuous, there was a very distinct drop in output, to much less than the Dorcy (RR switching to Moon Mode). I turned it off to let it recouperate a little, & it came back on brighter than the Dorcy, for about 20 seconds, then it dropped suddenly down into Moon Mode again. I did this several times. So, 9ish hours to 30+%, then a sudden large drop to very low levels. Is this more like a voltage boost, or current regulation? I'm sorry if this has been discussed before. I know the package claims that it is regulated. I searched CPF & found some threads that talked about it having regulation, but not definitively which kind, nor any runtime graphs. Anyway, very impressive, inexpensive little light!