I have seven rechargable batteries for my camera, and when there are lots of photo opportunities, I reckon each one will last for three days. That gives me three weeks of picture-taking if I pack them all fully charged.
If I think I'm going to be within reach of a plug socket every couple of days or so, then I'll just pack three camera batteries and the charger unit. That means I can have one battery in the camera, another ready to take its place, and yet another one in case I've seriously misjudged something!
If you're going with an organised party, I think you should be asking them whether you'll be able to recharge batteries on your particular route. If not, then the safest thing is to pack what you need, fully charged, for the duration of the trip.