charging - What is the best state to leave an Android device in?

I have a Moto E phone. I use it as a tablet to run apps, not as a phone, so I do not always need to leave it on.

Is it more likely that the device will last longer if I shut it off whenever I am not using it? Or is it better for the hardware of a phone to leave it constantly on, in sleep mode?

And is it better to leave it constantly charging, or to only charge it whenever the battery is below 100%?