I'm on my 3rd thinkpad. First one was a T30 that I got 12 years ago. I used it for 4 years and my mother for 4 years after that. I still have it and it still runs but it is now made out of parts from two T30s, the original, whose screen died, and another that had a bad hard drive. My T60p I used for 4 years and then my mother for 4 more years, it had to have its cpu fan replaced once about 6 years into its life, otherwise it is sitting here next to me in perfect working order.

I'm 3 years into a first gen X1 Carbon, it runs perfectly. The only annoyance is that I can't get at the battery to replace it. I'd be a bit happier if it had a 2560x1440 screen since then there would really be no need for an upgrade ever again, but as it stands I expect to be able to use it for at least another 5 years.

Build quality on the newer T series feels like shit to me, but I haven't spent enough time with them to be able to judge and they are so new we don't really have any data yet.

edit: seeing the link to the potential retro thinkpad, that I would get without a second thought

I use a W530 for work. It's a true beast of a machine. But I cannot stand the way all the plastic flexes. It feels cheap. I had to replace the keyboard the first week I had it due to a defective key (it happens, no big deal), but there's a little plastic strip at the top that was way to easy to bend and so now it's just ... there. reminding me of it's cheapness.

I have a T430s that I like quite a bit. When I was idly considering buying a T450s to get a higher resolution screen I looked into how easy it would be to upgrade the RAM and hard drive (much cheaper than buying a good one from Lenovo) and was disappointed that it seems much harder to replace them now.

triangle, how did you "upgrade" the MBP you mentioned? Once ram is at 3 gig and the hard drive is SSD, is there anything else to do?

the veep of design at Lenovo has publicly considered building a “retro” Thinkpad (with modern circuitry of course) — http://blog.lenovo.com/en/blog/retro-thinkpad-time-machine/