Our brains are like glow in the dark stars
To me, it seems that the human brain never stops processing a million things at once, it just shifts attention. It's like a CPU that never overheats. And from all the random science blogs/articles I've read, it seems that it is the least degrading component of the human body over time.
I'm sure you've experienced the scenario where you've racked your brain over a particular problem, only to figure out a solution the second you walk away. Or how great ideas come to you while you're in the shower or as you're about to fall asleep (or after waking up from a dream). I think our brains are like glow in the dark stars. They need to be exposed to light for a time. Later, in the dark, they begin to glow. A lot of time I find myself exposing my mind to the details a problem just to soak up the light. After I rest, there's a good chance a solution will have presented itself. (image from Flickr: http://www.flickr.com/photos/vblibrary)