Batteries have come a looooong way. Read this: http://www.dantestella.com/technical/mechanical.html.
My Mamiya 645 Pro is still running on the same batteries for at least the last 2 years, both the winder and the camera with a metered prism. Spare batteries and the hand crank in the camera bag. There are also low self-discharge NiMh batteries nowadays, search for "Sanyo Eneloop".