I have 4 x Olympus OMs in service at the same time loaded with Delta 400, FP4, Ektar 100 and Portra 400. Admittedly the cameras loaded with colour take quite a long time to finish the 36 exposures, but the B&Ws turn over quickly as this is what I mainly shoot. I also regularly take out a Zeiss Nettar 6x6 and a Mamiya 645, which are also both presently loaded and part shot. Moral - nothing wrong with having several cameras!