LCDs are definitely longer lasting than plasmas. I install TVs in sports bars where they are used 18 hours a day, 7 days a week. So this is an “accelerated aging” test for the use they’ll get in a home. Every single plasma has significant wear, aka “burn in” in places where network logos appear (thank you so much, ESPN). LCDs are free of this wear. They will get darker and more uneven as the florescent tubes providing illumination to the panel wears, but the panel will return to full brightness if you re-lamp it. When a plasma wears, the replacement cost of the panel plus labor will exceed the replacement cost of the unit. In bar usage, we consider 2 years standard for plasma replacement.
The number one reason for plasma over LCD has been black level. But the current generation of LCDs, especially the models from Samsung and LG, equals plasma black levels. The very best LCD technology, using LEDs as a backlight instead of florescent tubes, is even better allowing enhanced color and fully black areas of the screen.
Both LCD and plasma will ultimately be replaced by pure LED or OLED technology.
Don’t think you can fairly evaluate any TV in a Best Buy. For one, the environment in those places has nothing to do with your home. They are drastically brighter than your home, and in order to compete with that lighting and with the other sets, they are all set to a cartoonishly bright configuration, usually labeled “Vivid”. Change it to “Natural” or “Neutral” to get a more realistic view. Also, bring your own DVDs, because the material they are showing is almost all bright, and if you enjoy movies, you’re not going to see anything that features scenes in most movies.
It goes without saying that any place that won’t either let you use the remote to change the settings of the sets or play your own material doesn’t deserve your business. Visit a smaller, independent retailer that will allow you to do so and will have a more realistic viewing environment. And if you do, please, don’t be an asshole by using their time and expertise and going on-line and buying the same model to save a hundred bucks.