I bought one of these Coast Lenser lights at Home Depot for the same price last December. I thought it might replace my old Princeton Blast on my keychain but it's much too heavy and I fear from my car's ignition lock.
It's quite the torch for its size but as others have noted, there's no regulated power supply so the output gradually fades using regular batteries. The beam started to get a noticeably dimmer after about 3-4 hours of use. The stated 36 hours of battery life must be to zero output... so that is VERY misleading and a disappointment from a company that makes professional equipment. If they expect to sell a flashlight for $40, then they OWE consumers all the relevant data.
At this point I have to EDIT my original post since I'm remembering more of why I originally purchased this tac light. Which leads us here:
The COAST 2009 catalog says "LED LENSER'S Power Transformation Technology Overpowers Other LED Lights. PTT lights use a microprocessor to digitally increase the voltage supplied to the LED. At the same time, PTT regulates the current. This means a
brighter, more consistent light in a smaller package. For example, with PTT, you get the power of a 3 C-cell batteries from a single AA battery. Plus, because the microprocessor regulates the output, you get more consistent light over the life of the battery"
Because Coast throws around meaningless terms like "Power Chip", I originally believed that this model DID have a voltage regulator. But it seems of all their lineup only a few light actually have PTT. Given this light's actual performance... I have to assume it's not one of the chosen. So I now consider Coast's literature to be even MORE misleading. For my purposes I may buy a Coleman MAX… a smaller 2AA light that rates 111 lumens.
As for the Coast light… I'll be switching over to rechargeables... the poor man's power regulation. And while I may not quite get the rated output... it will stay the same until the voltage crashes and I get lost in the dark. LOL