In literature, it is just as useful to vary the style as it is in life to vary the thoughts. The risk of not doing so is to become addicted and diminished, narrowing horizons and dooming the next expression to be a replica of the previous one. To a certain extent, varying the style is also thinking differently, and the writer who gets used to doing this will be getting used to stimulating the brain so that it does not settle for what it has already conceived.