1. doing your bit for the environment
Lol! (Sorry)
2. preserving your battery life
Understandable, I suppose.
3. extending your phones life (theory) - ie the device/screen will have a life span
I don't think this would ever be an issue really.
4. Surely its not great to surround yourself with all those waves and signals 24/7
That is just rubbish the press have stirred up.
surely its makes sense that you should turn any electrical item off when your not using it? for me that would be around 11:45pm until 8am
Not when it is a communications device that is designed to be left on.