You can leave it on if you wish but personally I would say if you turn your monitors off you might want to turn it off too. I use a power unit with multiple switches for monitors and similar, or you could put it on a power unit where you plug in any other devices that don't have a power switch and shut off using that (if you have something like that in your setup). I would also disconnect it from your computer once you've loaded your measurements on to ARC Studio since any device connected via USB is a risk for bus noise, I'm a bit paranoid in that way but also ARC Studio doesn't need to remain connected once the measurements are loaded so it can easily be disconnected thus having one less wire / connection around