I go back and forth scores of times getting things right in the printing/beta test/design tweaking phase. As a plus, I end up with a lot of 2nds to practice my painting and weathering, or send to people who are ok with 2nds.
Exactly! Seconds or early iterations are perfect for trying out new paint or painting techniques. As you start getting close to the "production" version, the parts are good for doing test assembly of multipart assemblies (or a kit). I have a pretty good collection of assembled, but throw away models that were done that way.
I try to avoid giving people 2nds... I want them to experience the fully developed part, rather than having to tweak something that's not quite all the way there. But that's me...
Jeff