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%?
Looking at it from a battery point of view
Leaving the device in sleep mode is preferred , unless your usage is very infrequent
In addition, you can use Greenify (see greenify wiki) and Wake Lock Detector as explained here for unrooted devices
As far as ideal charging limits are concerned, you can see this and decide what suits you best Ideal charging / discharging percentage for maximum battery life?
Switcing off Wi-Fi and Bluetooth
Once your battery consumption is taken care off, there isn't any concern in leaving it switched on in sleep mode
"Should I shut off my phone when not using it?"
You must keep in mind that starting a phone consumes a lot of battery. So, you shouldn't shut down your phone if you are going to use it again in 15 to 20 minutes. Otherwise, it is a good idea to shut off your phone to save battery. But will it increase your phone's life? The answer is No.
"Better to leave it constantly charging?"
Overcharging won't have any bad effect on your phone. But if you really wanna increase your phone's battery life, always keep the battery percentage between 10% and 90%. It wil increase the longevity of your phone's battery by a lot.
