At our los angeles summer camp , we used to run 10 weeks but cut down to 9 for a few reasons, one of which is just what you're saying: it's not easy to staff those last few weeks! By dropping the 10th week we've lost some revenue but losing the staffing headaches was worth the tradeoff. Operating for 9 weeks has been a nice compromise; we generally don't have too much trouble staffing for that last week \:\)