For a head lamp I use a Stream Light
Clipmate ,it used 3 AAA .
The one I use has 3 green LED's so to not scare game and still be able to read a compass.
Both deer and turkeys seem to ignore it.
It can be cliped to a hat ,coat or used with the head band supplyed with it.
The batteries last over 80 hr ( I replace the batteries 1 time all last fall and winter )
They also sell it with white LED's
About $20
For a flashlight I use a
4AA PROPOLYMER® LUXEON® (thats the name and what it takes)
It has 7 blue/white LED's
The batteries last a long time ,I replace 1 time per season if needed or not
Not much bigger than a Mini mag light but brighter and lasts 5 + times longer
About $25
I would say if you carryed a extra set of batteries you would be good for 20 days.
I have used both for years .
I can highly recomend both.
I give them to freinds and family for X-mas
Johnch