For me when I work with poser and or Vue I start the machine on its render and then get up and go do something else like laundry or start the dishwasher, clean, something active, until the render is completed. This way it gives my eyes and body a break. Like you I am in bed by 11 and up by 5 but working in front of the computer makes a lot of people fatigued you just need to break up the time in front of the screen.

My Facebook Page