I also keep my MB-D10 on my camera. Not necessarily for the extra battery life, but for the faster burst speeds while shooting HDR as well as the feel for shooting portrait shots. I don't use a nikon battery in the MB-D10, but rather rechargeable AA's. With a set of charged AA's in the MB-D10, a charged regular battery in the camera, and 8 spare AA's in my bag I can shoot my brains out all day and not run out of power. Besides, I have fairly big hands and like the bulk.