You can leave a plasma television on for 24 hours a day, seven days a week. In fact, many airports use plasma televisions to display flight information and these are rarely turned off. That being said, if you don't want to shorten the lifespan of your television or rack up high energy bills, turn it off when its not in use.
As of 2011, the average lifespan for a plasma television is 100,000 hours to half-life, although the lifespan of many value brands is much less. Half-life refers to the point when a plasma television has lost 50 percent of its brightness. After its half-life, the television screen appears darker, images look washed out and contrast levels are significantly reduced. Since each hour your television is on shaves one hour off its lifespan, its best to turn it off when no one is watching it.
Plasma televisions produce a considerable amount of heat when in use. Although most include a built in fan or other form of cooling system to prevent overheating, excessive strain placed on plasma's cooling system can significantly shorten its lifespan and may damage electrical components within the unit. Avoid overheating by keep a minimum distance of eight inches between your television and other objects and turn your television off when its not in use.
Screen burn can occur when a static image is displayed on a plasma television for an extended period of time, causing a ghosted version of that image to become permanently seared into the screen. Screen burn can be avoided by zooming in the television's picture or changing the channel when static images are displayed, especially within the first 1,000 hours of usage. It's important not to leave your television on overnight or when no one is watching it because you won't know when a static image has been on the screen for more than 20 minutes.
Although excessive power consumption is not directly related to the health of your plasma television, it can be a costly consequence for leaving your plasma turned on too often. In fact, all electronics consume some power when they are plugged in, even if they are turned off. To save money, not only should you turn your plasma off when not in use, but you should unplug it as well.