I want my headlamp to be bright enough for night hiking, regulated so it doesn't start dimming before the batteries are gone, and capable of taking lithium batteries (last longer and work better in cold temps). This is particularly important in fall and spring with shorter days. In summer, I use a Petzl e+light which weighs only an ounce, and normally is needed only when I get up at night. I wouldn't like to do extensive night hiking with it, though, which is why I use my Princeton Tech headlamp in shoulder season.