I was in the elec repair business. Made my money taking care of this stuff. Here is what I KNOW and am not supposed to tell.
Plasma is a gas that does degrade every time the unit is turned on. If you Drop it (happened) your son jams a pencil through it (happened), your sons friend slings a baseball bat through it (happened) your housecleaner sprays solvent on it to clean it and it drips down behind the screen or on to the circut boards(happened) or a ladybug crawls in between the screens and dies leaving a spot with a yellow ring of decay(happened) your option is to replace the display or get a new one. If you choose to replace the the display (out of warranty of course, as none of these afflictions are coverd by warranty) and your repair place can find another display (good luck as most are spoken for for your natural life) and you have the 6 weeks to wait, please multiply the purchase price of your TV by 1.5 and that should be about right. The sheer amount of work to do the job is akin to taking a flaky pastry crust appart layer by layer, fan by fan(they put out a ton of heat, but hey, don't duct that room) board by board and then remove display, replace display and pray you don't break it, then put it back together. There are damn few people in the world who do this work and fewer who do it well.
They have a great picture, but they will die out soon (much like the local TV repair center). You can order a projector, extra bulb or two, movie screen material, go to radioshack and get the proper cable from box to projector, local lumber place for some trim, mount it on the wall, and when you are not watching racing or the game, you can give powerpoint presentations to your kids and inflict slideshows on your neighbors and still not approach the cost of a plasma, and with a couple of bulbs, triple or quaddruple, the viewing life of a plasma. While burn in is an issue on both counts, it will go away on a projector, plasma not so much. DLP and LCD nice and cheaper also. But if you want BIG, make a home movie house. I have seen it done and it is the way to go.