For over 20 years, I used one camera and one lens. Then, after joining RFF several years ago, GAS hit hard.
Now I have over 20 working cameras, and several dozen lenses. I swap cameras and lenses almost as often as I change film (or copy images off the memory cards).
Sometimes I stick to a single lens and camera for awhile, but then the neglected cameras and lenses call my name. I do really enjoy the challenge of using different lenses, from 18mm to 500mm.
I do not have a favorite camera or lens, but when inspiration gets very low, I go back to that original camera and lens, and start all over again.
There is an old saw that using one camera and one lens is very liberating. I guess I just don't want to be that liberated.
My favorite question is "What does this button do?"