The quality of the components joints and solder in computers has gone down over many years now so that they just don't last as long as they once did. That has gone in hand with them being seen as disposable objects . It's also why they're now pretty much worthless once bust where as they used to have a scrap value.
That's even the case in the £1000 + business machines unfortunatley.
But you guys all sound like my ideal users who actually take care of their kit.
2 month old iPad smashed yesterday when it was dropped in a van and hit the metal gear stick. 
Or there was the one that got run over, or the blackberry that was dropped down a festival portaloo, which they only told me after they'd slapped it in my hand. 