I'm yet to have a Mac laptop (come on Steve, announce something I can get my teeth into), but I'd imagine about two years. My little Sony T2XP is ticking me off after a year, but that's mostly down to Windows. I've got some old Dell Inspirons that must be getting on for five years, and another Sony Vaio that's about three, but I hate them all. Laptop technology, just like mobile phones, has changed rapidly and aged many machines before their time. Mac laptops appear to have faired better than most.