Getting a new build of your game exported can take quite a bit of time. It takes time to actually make the changes in the editor, then you have to export the game and upload a new version on each of the App Stores you are targeting. Then, you have to spend time waiting on them to approve the app and for everyone to actually download it.
One of the things I talk to my students about is creating projects that can be easily changed without having to open up the Unity Editor. This could be done using data-driven development practices--such as building levels or encounters using text files, Asset Bundles, or Unity's Remote Settings menu--to allow us to instantly modify variables in copies of the game that are already out.
One of the things we may want to be able to update is tweaking the difficulty of our game by changing the speed at which...