Before my Mac, I have had 4-5 labtops that have all failed on me. They lasted around a year or two before something gave out.
That's pretty consistent with my experience in fixing other people's hardware. The areas on cheap PC laptops that usually fail:
- Power connector. This is very, very common. Someone puts together a high power consumption machine with a cheap crappy power jack that melts the solder out where the center pin interfaces with the board. I suspect the usual initial cause is a crack caused by repeated jarring of the power pin that just gets worse until it fails to charge entirely. Not a bad repair, assuming you have the skills to fully dismantle a laptop, resolder the power jack, and reassemble it properly (which is beyond the tech skills of most people). I've obtained a number of "broken laptops" with something going on power-jack wise. Apple, since the Macbook era, has used the various magsafe connectors that are utterly indestructible. The chassis is a structural part of the plug, and they don't transmit force to the laptop because they just pop free. Brilliant.
- Mainboard flex related issues. This is often just a total failure of the laptop, or it gets unreliable, or some number of weird things. It may happen if you flex the laptop initially, then proceed to total failure. This is usually because on a cheap laptop, the mainboard is a stressed member and takes chassis loads. PCB does NOT like to flex. Throw a cheap PCB as a structural member of a flexible 17" laptop, and you have an impending failure. Apple has always built stiff laptops, and the unibody ones are utterly insane. They don't bend at all. The PCB never takes any stress. You can get a PC laptop with a rigid internal structure that performs similarly, but they're typically business-class laptops and cost almost as much as Apple hardware.
- Memory (RAM) going bad. This is, in theory, a problem for everyone, but I've seen it a lot more frequently on PCs. It's almost like if you are building a cheap laptop, you throw in cheap memory...
There are some problems that affect both PC and Apple hardware (the nVidia 8600m chip failures were a plague across the board), but mostly, Apple stuff just keeps working reliably. The hardware is expensive, but the quality is there to justify the cost.