I try not to have too many cameras with partial shot films in them. Right now I have 4 cameras/back and it's driving me nuts. I want to send off some rolls to get processed but I feel rushed in the rest to get them in the shipment.
So, what's your "max" bodies/backs to have loaded?
Before Kodachrome processing went away I shot at most three emulsions in 35 mm. KM for closeups with flash, an ISO 100 E6 for everything else in color and sometimes an ISO 100 B/W film. Since my Nikons don't have interchangeable backs this meant two, sometimes three, bodies. Nowadays, at most one. Except when I intend to use a long mirror lens and want a body with autoexposure and stepless shutter speeds on auto.
I used to shoot ISO 100 E6 and ISO 100 B/W with my 2x3 Graphics. Two rollholders did it.
Nowadays I shoot ISO 100 E6 on 2x3 and 6x12 with a Cambo. Two rollholders again.
It comes down to one body or rollholder per emulsion with, sometimes, a backup body or rollholder.
When I was shooting movies with crappy old used S8 cameras I always took a bunch so I'd have at least one that worked. A Beaulieu for when I needed what only it could do, a couple of Canons for when I didn't. And, eventually, a Nautica instead of an Ikelite housing for one of the Canons. The Nautica was smaller and lighter than the housing and, with its PMA shot wider in air than anything else I had.