DLP bounces light from a bulb off mirrors. Mirrors don't degrade, so it's true that in theory, there's nothing in a DLP tv to really break. That said, modern plasmas are rated at 100,000 hours to 50% brightness. And since most people don't have them at anywhere near full brightness, when it dims a bit (after a long time), they can just turn up the brightness. As for the "long time," if you watch your tv for 8 hours a day, 100,000 hours is 34 years.

Obviously though, infinite years > 34 years. So what's the catch? The bulb, obviously. DLP bulbs are rated (as I hear) at anywhere between 1 and 8 thousand hours, at a cost to replace of 2-4 hundred dollars. At 8000 and 200 (the best scenario), that's 12.5 replacements in the time it takes a plasma to get to 50% brightness (which again, isn't really 50% for most consumers since they can turn up the brightness), at a cost of 2500 dollars. In other words, yes, your tv will last longer than a plasma, but by the time it does so, you'll have paid enough in maintenance to have purchased a replacement plasma. Perhaps two or three, depending on what prices are like in 34 years time.

DLP gives a picture comparable to the other technologies and I don't think you made a bad purchase by any means, but. . .well, you certainly didn't pick the longest lasting technology, by any means.