my daughter's laptop PC has just come back from repair, it needed a new hard drive after 18 months.
During the 10 days it was away I used my old Macintosh LC75, built 1993, which I had in daily use until autumn last year (2007), and only stopped using for reasons not related to the computer (e.g. that computers at the library no longer have a floppy drive, which I needed to transfer files written at home).
I admit that the comparison is slightly unfair, as my Mac came out of a pool of maybe a dozen similar machines at the lab, and I picked it as my personal Mac in around 1999, so at that time any computers that may have broken down after 18 months would no longer have been in the pool. So it is a "survivor" by default.
But still, 15 years vs. 18 months, that is quite remarkable. The last laptop PC I bought for myself, back in the 90s, didn't survive more than 2 years either.