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Early 2009 iMac 24" 2.93GHz C2D is still going strong. I removed the Optical and replaced that with a Crucial 256Gb SSD plus upgraded the HD to 2TB (created fusion drive), upped the RAM to 8GB also. This should keep me going for another couple of years. I generally will upgrade when I can no longer upgrade to the latest OS which has not happened, yet... Hopefully the next OS upgrade will still be compatible.

Jeff
 
I update every 8 to 10 years. You don't need to update until the latest OS that you can operate on your hardware is AT LEAST two generations old. There are lots of games, updating your entire machine just so you can play Mega Droid 12 is just a waste. Use the money to take an extra week of vacation.

Well that is my wooden nickles worth.
 
I'm still rockin my 2008 iMac. It has the intel Core Duo, but I doubled the RAM to 4GB, and it does everything well minus 3D gaming. Really can't justify dropping the cash on a new iMac since I really am not a power user.
 
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