... I guess I gotta go earlier and bring more batteries for the headlight
I don't know how feasible it would be for you... but instead of carrying 400 lbs of spare batteries might look into rechargeables and one of those solar chargers gadgets. I know they sell them... and they're fairly lightweight. It would save weight on having to carry 3 weeks worth of spare batteries that are going to fizz out quickly in the cold weather.
