We never go out and buy the latest version of Windows. Microsoft is still working with bugs and patches almost until the next edition is rolled out. We will often even skip an upgrade until an even better version is available. We are still using XP as well and will probably upgrade with Explorer 10 comes out according to our IT guys.
The racket of making you install new software and buy new hardware every couple years is expensive and unnecessary. We run on 4-5 year purchase cycles and it works just fine for us.
I am working on a corporate conversion from XP to Win7. They had to package over 14,000 pieces of software for approved corporate installs on Win7.