I tend to buy boxes with fairly high end parts (not expensive, just high quality), and when I built them I did the same. High end enough that I really didn't have to upgrade until everything was no longer "state of the art", so no parts to recycle in.
My ooold computer has a Q9550 and 8 gigs of ram, just as I ordered it. It is still pretty usable as a daily backup video player, and not bad for midline gaming like Portal 2, Goat Simulator, etc. Upgraded the video 3 years ago, $150-175 for what was then a steal.
5 years old, and the CPU is still on the front page of Passmark, at >4000 pmarks. Not bad. Paid around 1800 without monitor. Upgraded to 7 Pro over Vista, but even the original install is intact. Hard to beat that kind of stability, and not convinced you can build it by hand anymore.