Yes they may last less or more but if you go to the usual makers you see the 5 year design noted. At the low end of the spectrum are common sleeve bearing fans with lifespans from some months so the overall number is now just a few months if you have the luck of such a part.
Does anyone know what the average lifespan of most hardware is? A ball park figure is fine. hard drive, cpu, motherboard, etc...
It's my general inclination when replacing hardware for a realllly old computer, which is not yet having issues, to start with the hard drive. Is this the right thing to start with?