I use my late 2011 MBP as desktop mainly, it sits on my desk connected to a USB keyboard, mouse, and hdmi adapter monitor. When I walk away from the computer, the screen goes dark after a few minutes and it seems to be asleep. However, hours later I will notice the fans are still running and the white led on the front is one continuously instead of slowly flashing. Is this normal behavior? If not, how do I correct it?