So when do you stop upgrading the OS version on older hardware? And why? Do you ever feel it's worth being "left behind" on upgrades in order to maintain your current functionality? Or do you push the upgrades until the hardware is no longer compatible? For instance, I am sitting at a Early 2008 iMac running OS 10.6.8. I suppose I could bring it up a few more versions of OS X, but I'm faced with having to update/replace/lose some of my existing software (Quicken 2006, Office 2004, pre-12 versions of FileMaker Pro, etc.). If I were to upgrade this machine, I'd probably want to do a clean install. Without physical media for all my software, this might be a huge risk (but I digress). I have a 2011 MacBook Pro that I could take to 10.12. I'd lose a couple of older programs I use occasionally for backwards compatibility which I could maintain on the older iMac. But how far out can you go before performance losses outstrip functionality gains?