I personally don't think you're timeframes encompass a broad spectrum of people. I know this is MacRumors and all, but really, who changes their computer out so frequently? Obviously based on your poll results thus far, not many. I usually wait until AppleCare runs out, and then try to time my next purchase alongside the next major release. I recently had to break that cycle though, as my trusty 1.83ghz Macbook Pro took a nosedive into traffic. So now I have a Unibody Macbook Pro, which I really feel like it's a prototype. That's especially hard to deal with, considering my 1.83ghz Macbook Pro was the first Intel mac ever launched, and despite only have a 32bit Core Duo processor, I never once felt like I was beta testing a product. Don't get me wrong, this Unibody is nice, it just some how feels "incomplete".