Agreed. The upgrade paths are not easy and it seems like as soon as you upgrade another version comes out. I almost feel like we test in production for K2. We pay a large amount of money every year to test K2 in our production environments. This is frustrating. 

Interesting how you guys disconnect each version to its own when each version release (4.7, 5.0, 5.1) is basically just an update to the base product like iOS 11.0 to 11.1 etc or Android 6 to 7. Base functionalities are still there, it still runs your workflows and smartforms, features can get deprecated and new features can get added, you get some new controls and maybe some services gets removed. It's all part of an application's life cycle. No application is ever free of flaws and that applies to every single one out there, patches are commonplace and I don't see why that is a concern. I would be more concerned if an application never ever receives a single patch.

If I may put words in the OP's mouth, I think we as K2 customers disconnect each version because the update does tend to cause development effort to get the forms and workflows back inline with the new version. Particularly the leap to 4.7 was problematic because it actually prevented bad rules on your forms and forced you to go back and fix them. I view this as a good thing, but it did cause a lot of extra work. I've recently upgraded a few different implementations from 4.7 to 5.1 and did not experience the issues that we had going to 4.7, it was a much simpler process overall and I've been pleased with the result.