I don't recommend having multiple consoles plugged in at once, I had a switcher once for AV cords, while it was nice but I outgrew it and no longer use them. I just plug in one console at a time now.
Keep in mind when it comes to leaving AC adapters plugged into outlets when not in usage. Nintendo warns that you should never leave an AC Adapter plugged in when you are not using it. I read this somewhere about the safety of the NES and the SNES mini. besides leaving your consoles plugged into the power can make them more dusty faster, since when their plugged in to the electric outlet becomes more of a dust magnet, anybody remember dusting off those old CRT television screens of the 1990's and 1980's?
I keep An Xbox 360 inside a cabinet unplugged. And I the last time I had a tech look at it he said it did not have any dust buildup inside, the tech said my Xbox360 was clean