My $12 headlamp died 40 minutes into a night hike near Estes Park and my backup saved the whole trip
Last month I was coming down the Glacier Gorge trail around 9pm when my main headlamp just cut out, no warning, nothing. I sat there in the dark for a second, then remembered I had tossed a cheap $12 backup light in my pack's hip pocket before leaving the trailhead. It ran for the full 2 hours back to the car and honestly threw a better beam than the one that died. Now I want to know, does anyone actually trust the battery life ratings printed on the box, or do you just test every light at home before a trip?
So the main one that died, was it a legit brand or one of those no-name Amazon specials with a 9000 lumen sticker? Because that makes a difference in whether I'd trust the box numbers at all. I've had lights that hit their claimed runtime and lights that quit at half of what the package said, and there is no way to know which one you got until you actually run it down. What bugs me about your story is the no-warning cutoff, not the dead battery itself. Did it just go dark all at once, or did it step down to a low mode first and you missed the signs? That tells you a lot about how the driver is built and whether you can even depend on it as a main light.
Did it just cut out on you with zero heads up, or did it drop to a dim mode first? That kind of sudden blackout would scare me too, especially if you were counting on it as your main light. @allen.kai is right that the driver tells you everything, and honestly a light that dies without warning is a light I would not trust in a real pinch.