Once you design your main look and feel of your app .. you may start adding new features .. that requrie new interactivity .. how to stay consistent with youe previous behaviours ?
closed as too broad by JonW♦ Aug 18 '14 at 8:56
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It's possible to reshuffle the design with every added feature, but it's inefficient, takes up a lot of time, and occupies your thoughts with individual elements.
A better alternative is to refactor once the strain of your current design becomes apparent, as then you get to look at everything at once, giving you a lot better picture of where things should go.
Of course, if new features are a common occurrence it's a good idea to design for extensibility, but even then it won't get rid of the need for regularly taking a step back and looking at the big picture.