Just looking for some opinions on the best amount of time to keep a machine before upgrading. For example, should I get a new iMac every 3.5 years? What is the optimal amount of time to wait so that you still get a decent price when selling your current machine? Obviously, the longer you wait, the more your current machine will depreciate, so is there a point that represents the most value when upgrading? FYI, I currently have a 2.16 Intel iMac.