My last laptop, the very first iBook purchased in Fairbanks (according to the guy at the store), lasted ten years. I will add the caveat that I maxed it out on RAM in the beginning, and swapped out its 3 Gb hard drive for a 20 Gb about halfway through, and during the last couple of years of its life, all I ever used it for (all it could really manage with OS X installed) was web surfing and text editing, while my main machine was a desktop. Still, I dragged it all over the continent, to conventions, to rural Alaska; I spilled a cup of tea and a glass of wine on its keyboard/hard drive, dropped it, froze it, got it wet, got it dirty. And it's still alive; it's just been gracefully retired in favor of its replacement (Fleetwood MacBook, which I'm currently typing on). I never had a virus, and I had only one hard drive crash necessitating an OS reinstall in the very beginning, which I think was basically just bad luck, since it never repeated in all the years I used it.

I loved that thing.