Well, my last TV a Sony Trinitron, I bought around 97 to 99 (not sure exactly) and kept it until last year when my g/f got an LCD (I also have an LCD and we don't need more then two tv's in the house). So unless it breaks I plan on keeping this sucker for a LONG LONG time. I will make the costs
Other then that, anotehr reason to get LCD over PLASMA are burn-ins. For those who play console games - this is a no brainer - unless you want to have perm burn-ins. For those that do not - you will still get burn-ins. I had a Panasonic Viesta (think thats the model) and after 8 months the top left blue box that appears when you turn the tv on or switch input types (it hangs out for about 5 seconds) burned in. This is a feature of the tv and pops up rarely - but it burned in. Other things that burned in - the little play triangle from a dvd player....which I rarely use. Also another image that only appears for a few seconds.
When I called Panasonic and asked them why a feature of their tv burned in, the tier 2 technical rep said "I cannot confirm or deny this is a feature of the TV". For crying out loud, it *IS* a feature of the TV, and it is one that *cannot* be turned off! Luckily for me I had circuit city extra warranty. I went to them they gave me store credit and I got an LCD. I play COD4 all the time and so far no burn-ins.
The difference between plasma and lcd is that LCD does not use true black and white - the only time I notice that are in very dark scenes (night) and you get the white haze. It doesn't bother me
For those that DO go for a plasma, my recommendations:
1) Do not play games or use features that linger
2) Once per week load up a picture (memory stick JPG, playstation/xbox stream from your computer, etc) of pure white. Let that sit for about 10 minutes. Yes it's annoying, but Panasonic says this will remove any ghosting. According to Panasonic ghosting is prelude to image burns which can be remedied.
3) Do not put anything that is repetative on your tv for long. So avoid playing video games, or hanging out on your dvd/cable menu screens (e.g. DVR screen setups, cable tv channel guide, etc)
Or - just do the smart thing (and environmentally friendlier thing) and by an LCD. You may not recoup the costs in a short period of time...but whats an extra couple hundred bucks when you are considering the environmental factors. If everyone went for the environmental reasons, and took that small loss of money then our kids/grandkids will have a better life....and you will have a better product.