Developing a Redux store as a seperate NPM module for a React App

Well, your app and its state are tightly coupled. When you update one, you need to update the other one in most cases. So you will have to update and publish 2 NPM packages instead of one each time you fix a bug or develop something new.

So I guess I would do that only if I needed the exact same store, actions and reducers in several apps. Otherwise I don't see any benefits to move the state of the app in another package. It seems like a lot of painful extra works for no real benefits.