As the great American Architect, Frank Lloyd Wright once put-it: "the jackhammer on the construction site is the equivalent to the eraser on the drawing board."
His caution should be your caution: explore your product approaches early and thoroughly. Industrial Design isn't just pretty pictures: it is the exploration of possibilities.
While inserting conceptual explorations into your product development timeline might seem excessive initially: viewed in the context of the cost of tooling, inventory, build costs, marketing and sales--it is a bargain in the long run.
Industrial design isn't just sketches and photorealistic renderings, but it is also a path to exploring how humans interact with things on a functional level. This is called ergonomics and it can determine the best placement for a knob, even the shape of the knob or it can ascertain the best way to present information on an interface and the best way to interact with that information.