I think it depends a lot on where the library is in its lifecycle. A new library should iterate rapidly and be very clear about that. Big warnings, obvious ve

I think it depends a lot on where the library is in its lifecycle. A new library should iterate rapidly and be very clear about that. Big warnings, obvious version numbering, and good communications. You look for an audience of actual users that can keep up with that. That's how you figure out what the right library is, both in terms of the big abstractions and the small details. But then once you hit a 1.0 release, things change. You're shifting from an audience of fellow explorers to an audience who wants stability. You can still do exploratory work, but it has to be additive in the 1.x series, and eventually you need to start a 2.x series as you learn more about what needs to change. So the iteration still happens, it just happens away from the people who just want the basic thing you got right via the initial burst of iteration.