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My iMac is 1 year, 3 months, 1 week, and 5 days old.

The HP Pavillion I use as a paperweight is about 3 or 4 years old.
 
I tend to sell stuff while they still retail some of their original value. As of right now my computer ages are:

MacBook = 1.5 years old
Windows PC = 1 year old

My previous Windows PC was 1 year old as well before I upgraded it, but my PC before that was 5 years old. Prior to that most of my computers were about 2-3 years old before I upgraded them. That's one of the most redeeming features of Windows PC's is that when they get old, all you have to do is replace a few parts and they're like new again. The oldest part in my current system is one of the hard drives that is 6 years old. My current system I expect to last another 2 year before I do any expensive upgrades (mobo, video card, etc..).

As for my MacBook, i'm expecting it to last me another 2.5 years. I have no real intention of replacing it early, since I don't expect it to do everything I use my PC for. I am, however, hoping that Apple will release a headless mid-range Mac with a user upgradeable video card, so that I can ditch my Windows PC once and for all. If not, then i'll just save up and waste money on a Mac Pro that I don't really need.
 
From my point of view computers are only too old when they no longer serve a purpose... so all of my computers are still relatively new for me.
Well put.

I usually use my computers until they die on me or are no longer useful.

My Macs seem to continue to work and work and work...

That's why I like new things like the MBA. It gives me an excuse to buy something new! ;)

The oldest computer that I still use occasionally, I purchased in February, 1985.
 
Toshiba Tecra 8000 - i believe it is about 10 years old.
300 MHz, 6gb hard drive, 192mb Ram(upgraded) , not bad for its time.
Still runs ubuntu quite well, although graphically it struggles with youtube.

My mac mini, on the other hand, is a mere month and a half old!
 
Mine is 23 days old (new Mac Pro). Before that, a two and a half year old PowerBook.
 
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