Agreed. I have a 2008 MBP that is still more than adequate for any task I require of it. And believe me, I put that thing through the ringer on a near-daily basis.
Unless you're a professional film editor or a gamer (and, in the latter case, I'm not sure why you'd be using a Mac), you really don't need to replace Macs every 3 to 4 years. Especially desktops. The desktop market has matured, and it is moving along at a relatively incremental, unexciting pace. There's surprisingly little difference between a 4-year-old iMac and today's iMac, aside from some relatively minor spec upgrades and a new port.
Unless you're a professional film editor or a gamer (and, in the latter case, I'm not sure why you'd be using a Mac), you really don't need to replace Macs every 3 to 4 years. Especially desktops. The desktop market has matured, and it is moving along at a relatively incremental, unexciting pace. There's surprisingly little difference between a 4-year-old iMac and today's iMac, aside from some relatively minor spec upgrades and a new port.