Usually a Windows laptop would last me for about 2 years. But only for about 1.5 years as a laptop, since battery would be dead by then. Here's the story of my last Toshiba's Satellite:
2 months: sound stops working. Unable to get into warranty since the coverage is not global.
1.5 years: Battery dies.
2 years: LCD cracked spontaneously. I was surfing the web, when suddenly an ink-like stain covered the entire screen... forever.
Repairing it was as expensive as getting a new laptop, therefore I bought an MBP. I teared the old toshiba down, drilled it to a side of my desk and plugged it to the AC and to an external monitor. It worked for 3 more years. The HDD failed, and I don't see a reason to get a new one.
This MBP is more than 2 years old, and it still is going strong as day 1. It's pretty impressive how even today still delivers solid battery performance. The history goes as follow:
1 month: Keyboard was making a nasty sound, Apple changed it without asking a single question.
3 months: Sound stop working. Apple changed the logic board without asking anything.
15 months: Dropped it while on Europe. 5 days later the HDD fails and Apple repaired it without a single question.
23 months: Dropped it again in the same exact corner. Nothing so far....
I'm more than impressed. Not only by the global coverage of Applecare, but because the computer has endured two drops, with only a minor dent.