The Kontakt upgrade mill is the biggest scam going. You can't buy old versions, so every new library developer who jumps in does so at the current version, and any products he creates can only run on the version he used to create them. It doesn't mean he actually
needed any of the features introduced at the current version. Most Kontakt libraries available today would have been happy running under Kontakt 2, had they been created with that version.
NI helps to enforce obsolescence by making sure their own products are not backward-compatible, even libraries meant for earlier versions. They've gone as far as releasing fixes to their own libraries - individual wave files! - that were incompatible with the previous version of Kontakt. Even Microsoft isn't that arrogant.
For myself, I am a foot-dragger when it comes to updating software. I just gave up SONAR 8.5 this month. I stayed on XP until I got a library that was too big for it. Although I had jumped on K3 right away (for the choirs) I stayed on that version until a must-have library came along that required K4. I stayed on K4 until a must-have library came along that required K5. I will do the same when K6 comes along.
In 1992 I traveled to a place called Baguio City in the mountains of the Philippines. They had just experienced a massive earthquake. The city and the roads leading to it were still in ruins. A new high-rise Sheraton hotel had pancaked, World Trade Center style, killing hundreds. Landslides had destroyed a large new housing development, luckily still under construction and uninhabited. Needless to say, I was just a little nervous. So I found the oldest, most threadbare hotel in town and that's where I stayed. It didn't have A/C or reliable hot water and no Starbucks in the lobby. But it had seen a century's worth of earthquakes and was still standing.