Only had one camera for nearly a year. I have two lenses, but only use one of them - the wider. It wasn't a 'roughing it' ideology for making better pictures, it just ended up this way quite naturally.
It is commonly known that being good requires consistency, and at least in documentary style work or photojournalism, the most logical course begins with having a consistent optical output and frame size. Landscape photographers tend to follow this logic too.
However, a lot of art photographers working with traditional photography like to play with the medium and have what you might call 'kaleidoscopic vision' as a result. The 'final piece' becomes almost a collage of formats, which can be great, but the medium can become the message.
If you have lots of cameras and find yourself using them all, there's no point in punishing yourself, just learn how to edit your output into something cohesive! It's not rocket science.