As a long termed (enthusiastic) customer I’d also like to mention that despite having a service contract or not your main license will obviously never expire. So say you purchase a Standard edition license then you can continue using that no matter what, even if your maintenance contract would expire.
Of course it’s much more beneficial to have support, also because plenty of new and interesting features find their way into the program.
Note that code generation and import is only supported by the Standard edition and up. So: code generation based on your diagrams, and of course the other way around: the ability to diagnose code and then generate diagrams based on that.
Hope this can also help out a bit!