FWIW, I'm not sure the lumen rating really says much. The figure given is often "goosed" a bit by the marketing dept. And it doesn't really tell you a lot about the actual performance of the light. IMO the measured candela is a better real-world indicator of output. Candela is the intensity of light that actually radiates in a given direction vs the lumens which is the total light from the emitter. A somewhat sloppy analogy would be shaft horsepower and horsepower at the rear wheels. Some companies list the ANSI lumens and candela.

Coming back to WMLs for a moment, something like a Modlite will have a rating of maybe 1200 lumens but 60,000 candela. That will subjectively smoke most Chinese lights that claim 1,500 lumens (at perhaps 15,000 candela). Much of this comes down to reflector design, etc.

When the rubber hits the road I'm not super hung up on how bright a headlamp is; I'm much more concerned with run time. I avoid the highest level most of the time and go with MED to LOW, and certainly as low as I can go and still see what I'm trying to see. Sure, I'll take my "flamethrower" lights out to the woods to play with them a bit, but most actual tasks I use a headlamp for don't require so much power. Especially if there's a full moon out!

Of course, if you're a spelunker or do long night hikes perhaps there may be times more output would be helpful.