My in-laws have a 2009 iMac that's still going strong. Last year I replaced the HD with an SSD (nervously using suction cups to get the screen off while my F-i-L watches over my shoulder...)

My wife's 2011 MBP also gained a new lease on life with an SSD.

Similarly, I put 8GB ram into my 2009 iMac (I like the 24-inch screen), but only needed a 256 GB SSD. I'm quite satisfied and glad the machine has lasted this long.