I'm with Hawkbow, I love the little Energizer brand head lamps, I own a bunch. I've used them as my main light while navegating through the swamp tooling along in my small mud motor boat. I can't speak to blood tailing with them, but they put out plenty of light to get a bead on those darned raccoons when they try to get into the chicken coop at 3 AM. I usually get more than just 15 hours out of them, but I'm not trailing blood either. Guess it depends on which mode you use them in.
Swamp