I bought my Sony LCD about 4 years ago, it's only HD ready as opposed to full HD, but I won't bother replacing it until it dies, whether that's in six months or ten years.
Bought a Sony DAV-S550 HCIAB roughly the same time. I gave this to my parents when we moved home early last year. They love it, but I wanted to 'up my game'. My current stuff is great, and again, I won't replace anything until it croaks.
Hi-Fi wise (slightly off your topic, I know), I bought my Arcam A65+, CD72T & B&W speakers in summer '02. Only yesterday did I upgrade my CD player for a better one. Amp'll be next, but may not happen any time soon. Speakers will be last.
I have upgraded interconnects (from VDH 'The Bay' which were free when I bought my CD & Amp, to Kimber 'Silver Streak's, about 3 years ago), Power cables, mains block, Rothwell attenuators (Only a month or so ago). So you could say that there has been gradual upgrading of the stuff around the core components.