If you have trouble sleeping this is a bad idea. Studies show that leaving the tv on while you sleep messes with your internal body clock and also the melatonin in your body. The lack of light in your room helps release melatonin which is a hormone in your brain that controls your sleep cycle.
Studies have also shown that mixing that place where you sleep and watch tv is also a bad idea because when the tv is on, your body doesn't automatically get the signal that it's sleep time.
But honestly, I used to sleep while listening to KTVU's Dennis Richmond. He has a very smoothing voice that calms me.
I try to set the timer to my TV when I'm ready, but sometimes I fall asleep too fast so its on the whole night. Maybe I can save on my electricity bill?
I've tried it a few times, and I always end up getting too interested in what I'm watching to fall asleep. I pretty much need total darkness and quiet in order to sleep.
Rule of thumb: Keep your room dark.
But honestly, I used to sleep while listening to KTVU's Dennis Richmond. He has a very smoothing voice that calms me.