You guys are certainly giving me a lot to think about. I like the sound of the specs on the Zebralight Sc60- I'll also check out the Thrunite Nuetron 1A. It sounds like between these lights and a Quark A or AA I probably can't go wrong- just need to make a decision. I'm really going to have to do a runtime test on my HDS twisty on low and see how long it will run. The problem is I use the light all the time so it's kind of hard to free it up that long- perhaps when I get my new light I can test the HDS (I'll be sure to post the results).