I have my TV on all the time, I live alone and like the noise. Like really has never been off in 5 years except when the power went out.
With our old TV, we were told to keep it on 24/7 because it kept dust off the tubes and we had that TV for 20 years, but I don't know about the flat screen. I do keep it on 24/7 because I'm here all the time and do watch certain programs. Plus, at night I don't sleep well, so I put it to a station I want to watch. That puts me to sleep every time! But as soon as the cable goes down, I wake up and that's upsetting. Also, if I have a Dr. appt., having the TV on makes people think someone is still home (we have 2 vehicles).