I would agree, a laptop lasting 7 years is rare. It happens, **** I still have my compaq from 2000 and it runs great. I also still have my HP from 4 years ago and haven't had to replace a single component (the compaq i had to replace the hard drive 3 times all within warranty).
I don't know where you are going to school at, but a Windows based system would be much easier to work with for programming and school. Don't get me wrong, before someone flames me. You can definately program within the Mac OS, you can also run most of the programs your school will give you within the Mac OS environment. But what your teachers will be teaching in, what your examples in your books will show, and what 100% of the software programs they give you will be compatable with is the Windows OS.
Again, this isnt' to say you can't use Mac, i'm just saying you are far less likely to encounter issues and there won't be as large of a learning curve if you use Windows since all of your examples, teachers notes, and software programs will be windows based.
My major was computer information systems from 2000 - 2003 and while that was a long time ago, everything we did was within the windows OS environment.