Personally I would love to work at a overnight camp.
I worked at a varierty of camps with different lengths, I would say my favorite would be either 10 days or 2 weeks long-- because it is long enough to get to know your campers but enough where everyone gets a few days off
I voluntered for a camp that was one week long and its too short in time-- you only get 4.5 days of camp activities before you have to clean the whole site up for the next weeks camp