Oops - I've just bought it and dropped it. It will not now work.
It's dead on arrival.
A component fails at any time between a day and 10 years plus.
It's got too slow for modern usage and has had to be retired but still works.
Something new has come along (especially a game) which your system is not up to.
this is the point - the Harware looks perfect, its not dead on arrival, the components (Motherboard and CPU) do their work absolutely without any problems, the system is stable. So I get the impression - the laptop will not fail for eternity. But eternity is defentely exaggerated. The point is - I am realy satisfied with the system I use today (Linux and Windows XP). And I know for sure, that in the future I will not need Software which is not avalible for the operating systems I mentioned. That is why it is extemly important for me to konw how long the hardware will last if I use it 5 hours daily.
I'm running an 8+ year old PC, recently upgraded, from XP to 7, as I spend a while on the Net and XP will be getting progressively harder to keep secure.
Regular Housekeeping keeps it as fast as it ever was, but that is not as fast as the latest models, by a long mile. However, apart from beefing up my Back-up Policy, I'm expecting it to see me through to Windows DIX if I don't like the look of Windows 9.
The only thing that you will need to worry about is that any new peripherals, that you acquire, may not be compatible. However, the solution to that is to buy replacements on the Second User Market.
It is simply not possible to give an accurate answer to your question, only a statistical one. Product failure can be plotted on a graph and shows it to be a "bathtub curve" (can't draw it here so look it up on Google)where failures occur largely at the start of a products life due to poor manufacture. They then fall off rapidly and remain very low until the product wears out at which time the failure rate again increases to a high level.
These are however just statistics and can not be applied to an individual item, that is in the lap of the gods.