Linux improves so fast, personally I could not stand it to be using the OS from 5 years ago. If it comes to that to run some legacy application, I'll set up a Virtual Machine to run just that application.
I agree, and we tend not to run systems longer than 2 years without an upgrade. However there's nothing cozier than a nice, warm, security blanket! ;-) It's the *forced* upgrades that bother me. We've had the Red Hat rug pulled out from under us and this is causing me some pain...
-Fred