Listening to Time Brown, I agree with his point of speed prototyping. The faster you make the object, the faster new ideas come in. Prototyping may take a long to create depending on the design and sometimes when you make the object according to the prototype might not turn out to function or you might end up disliking it. That is why I think Tim made a good point in the speed prototyping.
“To get the most out of design thinking, design everything”