What is a good reason to build a robust model?

Building a robust model is primarily beneficial for parts that will be reused over an extended period. A robust model ensures that the design is reliable, adaptable, and can withstand the rigors of multiple uses over time. This focus on making the model durable and versatile supports maintenance, updates, and integration within larger assemblies or systems, thus enhancing its long-term viability.

In contrast, the other options do not align with the primary rationale for creating a robust model. Reducing initial design time may be important in fast-paced environments but does not necessarily require a robust model, as a quick prototype might sacrifice long-term durability. Similarly, when developing a prototype that is not intended for production, the emphasis shifts toward speed and experimentation rather than robustness. Lastly, while creating aesthetic variations may enhance the visual appeal of a product, it does not directly relate to the structural integrity or usability over time, which are key considerations for a robust design.