I bought an $850 Thinkpad T410 in 2010. Every time I've checked new laptops in the past couple of years I concluded that it wasn't worth upgrading - I'd only get a twofold increase in performance for $800+.
(Also reduced weight and increased battery life, but as a 6 ft. guy with a roommy backpack, carrying a 5 lbs laptop and a 1.5 lbs spare battery is not a problem.)
It still works fine but I ended up buying a higher spec'ed* mint-condition refurbished T410 for $250 this year, and a USB3 expansion card. I expect to get a good run out of it since I can cannibalize the old one for parts.
Not everyone has the time and know-how to service their own laptop, but for someone who does, like me, the nice thing with the Thinkpad ecosystem is the abundance of cheap end-of-lease refurbished parts and accessories, which are i) cheap and ii) probably better maintained than what you can get used from some bloke on craigslist.
(But the flipside is that new Lenovo parts and accessories are horrendously overpriced, since they target businesses.)
*HDD vs SSD, 8gb vs 4gb memory, i7 vs i5, 1400x900 vs 1280x800, discrete vs integrated graphics.
I have a PC at home, almost passing the 5 year mark now. No problems with it, fast enough, plays the latest games. Only problems I've had with it was corrupted memory banks, but I'm inclined to think that's more to do with installing it myself than anything.