My ThinkPad T60 will be 8 years old in November and is still my main work machine. I haven't replaced a single part on it and the only modifications have been to max out the RAM and move from XP to 7 a few years ago.

I like the 14" 16:10 display much more than the current widescreen displays, and also the compact size for travel. It'll get replaced within the next couple of months, almost certainly with a T440P, but in part only because Windows 7 won't be available on new machines after ~October. I'll enjoy the new machine with an i7 and SSD but I'm going to miss the T60 that hasn't skipped a beat in nearly 8 years.