Depending on how you use it, between 13 and 20 years. The lifespan of plasma TVs is measured relative to the half-life of its phosphor gases. Half-life is the point at which plasma manufacturers posit that the picture brilliance has diminished enough to make a very noticeable difference in picture quality (and possibly merit replacement). Half-life, then, is the true halfway point in the lifespan of the product. Since these gases decay at a constant rate, the color intensity of your TV picture will decay at a rate equal to that of its phosphors. Think of this as phosphoric dissipation. Beginning the moment you turn your plasma TV on, the phosphors encased within its screen begin to slowly dissipate, so less and less of the total phosphoric content is available for ignition. This affects the display's brightness and color saturation levels. After 1000 hours of use, the plasma monitor should have retained about 94% of its original brightness level. After 15,000 to 20,000 hours, the monitor should measure about 68% of its out-of-the-box brightness. Which is to say, about 68% of the phosphors in the TV will be ignited to produce an image. Much also depends upon the contrast ratio setting used to view the unit. If you want a plasma TV to last longer, simply decrease the CONTRAST option in the menu settings. If you tweak the CONTRAST to 100%, you should expect to burn its phosphors out at an increased rate. As for the specific life spans of individual plasma display units, most manufacturers contend that their TVs last approximately 30,000 hours before reaching their half-lives under "normal" viewing conditions (i.e., with the CONTRAST set at around 50%). Recently, several manufacturers, most notably Sony and Panasonic, have begun to claim that their newest plasma display panels now have half-lives of 60,000 hours. I, for one, am a bit skeptical of such assertions, if only because this would represent a 100% increase in the life of the product. While I realize that much is being done to increase the life spans of plasma TVs (such as increasing the resiliency of green phosphors), I'll believe these figures when I see them achieved in real life, not just theoretically. From the consumer's perspective, though, the 30,000-hour figure should be comforting, since this is about how long CRTs last. Let's put all this in perspective: Assuming the average American household watches 4 to 6 hours of television per day, a plasma display will last between 13 and 20 years. If you think about it, that's quite a bit of bang for your buck. Following here are some guidelines you should implement to ensure that you get the most out of your plasma display: -Keep your BRIGHTNESS and CONTRAST levels "normalized" to actual viewing conditions. Don't jack up your CONTRAST levels unnecessarily; this only dissipates phosphors faster. In brightly lit rooms, you will probably need to boost your CONTRAST settings. At night or in other dim circumstances, you should lower these settings to extend the life of your unit. Note: Many high quality manufacturers now have added preset options to make this adjustment possible without even going into the menu settings. -Do not leave static images on your display for extended periods of time (i.e., 20 minutes or longer). This will prevent burn-in, which is a permanent after-image on your screen. -Turn your plasma TV off when it's not being viewed. -Keep your plasma television in a well-ventilated area, so it will not have to work so hard to cool itself. This is one way to ensure your plasma's cooling system will remain in tip-top shape for the life of your unit.