I think the reason you stated for why Mac machines have a longer lifecycle is true in part, but the technology actually changes very rapidly on the PC front. My old clunker PC is more than 3 years old and cannot be upgraded past the point of perhaps a new graphics card. I would literally have to throw the guts away and start afresh. I bought an iMac last year, and since going mac I will never go back. I now use the PC very occasionally as it generally gives me headaches, and screws up for no apparent reason on a daily basis. The Mac just lasts and lasts, and thats why people hang onto them longer, the old PC just runs like a dog unless you keep the same old buggy systems running on them. Every time Microsoft releases a new operating system, it requires you to use hardware made for the system, and if you don't you are just asking for headaches.
