Well i think every year is a bit much, i would say every 2 years if your really using it or if your just using the web, email, and stuff like that you could wait out every NEW OS release, seems to be every 4 years or so.
Well a 7 y/o mac can run osx tiger.. so you tell me? haha apples the best this is my first mac (macbook pro) and Ive yet to be letdown.. it jsut keeps getting better.
depends on how much u like computers but for me I like to change my comp every 3 years... apple computers will last forever they are solid... and get the new macs and get windows it makes things easier. play your games and do ur work its perfect
