It depends on how you treat them. Mine die every ~2 years or so. My father has had his for like 5. Then again, my laptop lives in my bookbag, my dad's doesn't leave his desk. Mine has all kinds of scratches and dings and discolorations from heavy use on it, his is basically in mint condition... I use mine for hours a day and often tax its hardware in various ways, he checks his email and watches Russian TV on it in the evenings.
I actually gave my last laptop to my parents because its video card was failing and (my guess) every time you moved it a wire or something came loose or something in the video card and it crashed violently. It's been sitting on my parents' dinner table for the past 8 months (and they've been using mostly it) or so and they love it lol. I guess one man's trash is another man's treasure...
Of course, if you get stuck with a poor model it can break quite a bit. But if you've had it for two years and haven't had to send it in for repairs/scrap it odds are if you treat it nicely it'll serve you for quite a bit of time more. If you've had to send it in for repairs that's typically a bad sign.