Most important factor to consider when storing a camera; is to ensure the area is dry, moisture free and it is a dust free environment. otherwise, you can breed Fungus spores.

I collect old camera and they are all kept inside a Velvet Lined wooden box with Silica Gel pouches chucked in the box to ensure that any unexpected moisture is absorbed.

Cameras that I use on a more frequent basis, I never store inside a bag, box, cupboard or shelf.

They sit constantly mounted on a tripod, in a corner and out of the way. I just throw a dust proof cover over them when finished and pull the draw string at the bottom. As the room where they are kept is dry with no humidity, I have nothing to worry about. In fact, I may even keep a camera on the shelf in the same room if all tripods are used up.

This includes cameras that I take outdoors for a shoot, when I come back, the lenses which are always inside their own protective cases each with silica gel, (which I do change from time to time), go on a shelf and I generally leave one camera with a Kit lens of 28-70mm on the body mounted on the tripod, always parked in “P”, as you say, for convenience and also speed of requirement! you never know what the kids may do next or the cat decides to do something equally amusing!

Keep your cameras away from Dust, Humidity and moisture and they will be fine.