recenly used Petzl MyoBelt, it uses 3 AA batteries and manufacture claims it lasts 80-170hrs (in max(85 lumens) or economy mode(70lumens) )
my experience so far
1. battery slot is not on head and headlamp is lighter, and for colder races you can put battery unit inside jacket for longer use
(v good for mountaineering)
2. economy mode was good enough to run clearly through night,
3. sometimes the battery unit makes it clumsy while running, but you get used to it.
4. buttons to change mode were small, found it hard with gloves on(I dread using it with mittens)
5. quite pricey but hopefully will recovery using rechargeable batteries
Overall, I liked the long battery life and strength of headlight. I recommend it.