If you can get a new Pioneer 5080 for $1300 it's a no-brainer. At your viewing distance 1080p doesn't matter, you don't have any 1080p sources anyway. If you do pick up a Blu-ray player at some point I promise you it will look stunning on the 5080.
You don't need to worry about burn-in, you will get temporary image retention that will fade to nothing very quickly, usually less than a minute.
The picture quality will not degrade any faster than an LCD, both are rated at 60,000 hours to half brightness. Some of this year's models are rated at 100,000 hours. I've had my Panasonic plasma for two and a half years and the picture is better now than it was when new.
The measure of a man's character is what he would do if he knew he never would be found out.