Strangelove

But if you leave it in it will spin up every time you boot the console, even if you're not going to play the game. Taking it out means it only spins up when you actually want to use it limiting your risk.

Not that I think that's true. I had heard that 360's can ruin discs when the console is stood on end, but I don't know if that's true either.

All I know is there was that 'whirr' from the disc tray you got when you turn on an old 360 and because it could be temperamental, there was a chance it could damage the disc. Put together a friend saying that someone else's disc had been damaged by that, my own experience with a disc becoming wrecked that way, all the horror stories about early 360 technical problems and my own cautious OCD nature and that is what you get.

It was absolutely proven by a Dutch TV show that tested 360s on a solid, level surface - discs were scratched in long circular tracks. Then, 360s have at least 3 brands of drive in them. FWIW my Elite (Jasper I think) has always been vertical with 0 problems so far.