I have a Sony Bravia 46" LCD and a 60" Pioneer KURO plasma, for about a little over 2.5 years. The Pioneer plasma doesn't have as much burn-in compared to respective 2008 models, but the technology to prevent burn-in for plasma has gotten better the last couple of years.
As far as 3D TV goes, I'm not too keen on them and I don't believe they'll go mainstream, at least within the next few years. For one thing, you need the goggles and for sets that don't require them, you have to stand/sit a certain distance away to get the full 3D effect. Let's say front and center, 8 feet away. Also, if you're prone to motion sickness or eye problems, 3D isn't the way to go.