When asked this question I remember the story of the veteran lumberjack who is proud to say that he still has his original axe - of course, it's has 4 new handles and six new heads but it's the same axe!
Computer technology keeps on changing at an ever increasing pace. The standard lifetime of a particular desktop computer model is approximately 18 months, sometimes as short as 12 months. At the end of that period the computer model you bought will won’t be on the shelves and replacement parts will become increasingly hard to come by. Try this yourself, look up and attempt to replace a motherboard, RAM, or processor which is more than 4 years old. No lu