So I don't know why this thread petered out but I still don't feel like I know what travelers do in practice. I'm going on a photo-safari and bringing two DSLR bodies so each camera has a spare battery. The rules quoted above seem to say that that's my limit. But nowadays people have a lot more electronic devices than just cameras - and we're going to be out on the bush where electricity will be scarce so what do most people do?