I have sold my Macbook from 2006 to a friend of mine almost 3 years ago, and it is still going strong. My current Pro is 2 years old and shows little or no signs of wear itself either.
With Care, a Macbook should last quite a while. Just try to keep it clean, and try not to drop it too much and you should be good to go
Welcome to the Universe, just as well welcome to MacRumors!
My iMac is 4+ years old & still looks & works like new
Ditto my 2 year old MBP - I still think of it as brand new & it surprises me when I realise it's got a couple of years on it.
I guess the MacBook will be more susceptible to scratches, as it's poly rather than aluminium, but get a slip case for it & it will always look like new
I am writing this on a 2005 G4. This thing is just as snappy as the day it arrived and I took it out of the box. It is an eMac with an old CRT display and is running OS X version 10.5.8. When I bought my first computer in 2001, I was totally ignorant about computers and I didn't even know that there was such a difference between a Mac and a PC. I actually thought that an Apple computer was just another brand of PC Lucky mistake on my part.
They will be obsolete for years before they no longer work. Actually, I have a powerbook from 1998 that still runs on Mac OS 9 flawlessly. It can't handle the internet anymore, though!
Any computer that you take good care of will last a long time. My roommate is using a Dell notebook that he purchased in 2004.
Instead of a Macbook, get a Macbook Pro 13" from Microcenter (if you live near one). It's the same price ($999) and is much better in terms of power and build quality. Alternatively, the difference is $150 when buying through the Edu store.