My old 15in MacBook Pro lasted three years of hard labour, going out on site with me most days in addition it was constantly being opened up and various internals swapped in and out. In the end the case was pretty beat, the optical drive had been transplanted, the sleep light was gone, the hinge was floppy and there were various other maladies. A hard three years.
So now I've replaced it with a lovely 17in MBP. So far it's rocking but it has a lot to live up to. The old 15 was easily my hardest working Mac ever and it never missed a beat, despite the alu MBP being generally though of as fairly fragile.
I'm hoping the 17 will proVE to be just as tough.