A typical plasma television has a half-life of about 30,000 hours (some newer high-end units now claim up to 60,000 hours). This means that it will lose approximately 50% of its brightness during that time. Based on a 30,000 hours rating, if your plasma television is on for 8 hours a day, its half-life would be about 9 years–or, if on 4 hours a day, the half-life would be about 18 years. Keep in mind that a standard television loses about 30% of its brightness after about 20,000 hours.