Originally posted by Wasp From an accuracy point of view, rocking three cameras doesn't make a lot of sense. I have tried that and it gets awkward and old very quickly. Too may bits of gear swinging around your body and slowing you down. Two cameras just work better.
The main reason for using multiple bodies is that you don't want to waste time swopping lenses in the heat of the moment. Having Pentax and Nikon could work for that. The other reason in the film era was to have monochrome in the one body and color in the other. In that use case, having two different lens mounts makes no sense.
In the 80's and 90's I always showed up for work with three 35mm SLRs. Sometimes it was because of different films, always three primes, so it was faster to switch lenses, and sometimes it was so that when one ran out of film, you could switch to another and not lose time rewinding and reloading in the heat of shooting.
No I didn't like it and yes there was always a strain on my neck and shoulders, but I was young and you never heard a photographer gripe about it. It meant you were working and being paid well enough. It was also a contingency plan to have the redundancy in case one camera stopped working.
Back then, that was often what separated the pros from the wannabes. One camera? Hobbyist. Two cameras? Ambitious part timer. Three cameras? Pro.