It's probably not the safest idea to be out in the woods, or swooshing down a mountain on skis, in the middle of the night. Unless you've got Petzl's upcoming Ultra Rush headlamp strapped to your head, with 700 lumens to illuminate everything that goes bump in the night -- or that you might bump into.
For comparison, an LED MagLite powered by three D-sized batteries produces just 131 lumens, so this lamp blasts forth a surprising amount of light given its size. There's no pricing or availability details besides a vague promise of a 2013 release, but the Ultra Rush will apparently come with a rechargeable battery pack and four brightness levels. And it's safe to assume that when set to its full brightness level of 700 lumens, the Ultra Rush's battery life will be severely limited. Which is why you're able to turn it down during those times you don't need to simulate daylight in the middle of the night.