Question: So I have 2 questions actually: But basically I have a 570gtx hooked up to my monitor via DVI and my 46inch LED TV through mini-hdmi on the GPU.

First question: Any harm in leaving it hooked up? Even when the TV is off. My mouse will still go over to the screen next to it. It also seems like my GPU fan is spinning faster even with the TV off (Any reason why this is).

Second: is there any way I can have some sort of button to switch between single monitor (when my TV is off) that I can click to switch to expanded monitor mode when the TV is on? Instead of pulling up the Windows display screen and disabling it every time I turn off my TV.

Answer: 
Use the `Windows` + `P` to be able to select between different video modes "Computer Only", "Duplicate", "Extend" and "Projector Only"

I have my monitor and TV connected to my two DVI ports and just leave the setting on "Extend" but if you wish to only have a video feed going to your monitor when your TV is off, just select "Computer Only" and you will no longer have the issue of your mouse getting lost on the TV by accident. When you wish to put something on the TV you can select "Extend" to be able to drag windows over to the TV or you could select "Projector Only" and have your entire desktop move over to the TV. If you use "Duplicate" both windows will be adjusted to the highest common resolution, which may not give the best image depending on the specs of your monitor/tv.
1. When the TV is off but the computer is still configured for two monitors, it will still require the processing power for the TV screen. Higher GPU usage is most likely because you have Windows Aero enabled.
2. You already have this feature with `Windows` + `P`. You can select which monitor mode you want. In your case, it would be "PC Screen Only". When you want both screens, use `Windows` + `P` and select Extend or Clone