With what seem to be very isolated issues of burn-in. What are your thoughts on leaving the display on for extended periods of time? Specifically, 2-3 hours. I have a thunderbolt to hdmi that I run to my TV to watch movies. Unfortunately when I do this, the iMac monitor doesn't turn off. I'm a little concerned if the extended time the display is on will cause burn-in or other issues. I've googled and searched and believe there is no possible way to turn off the iMac display without disabling the extended TV display. Thoughts?