With the exception of MIDI 1.0, software projects tend never to reach a point of completion.
One of the lessons of The Mythical Man Month is to plan to throw (the first) one away. Conway's Law and microservices architectures carry this idea to the extreme by encouraging the development of services that are so simple as to be disposable.
Maintenance is expensive. Embracing this inevitability frees us from the burdens of API evolution, feature deprecation, bit rot, regressions, and the endless frameworks du jour.