Let's say that a project has a delivery date in six months. Working backwards, that is one month to assemble and debug and fix anything that is majorly broken. Two and and a half months to have all components fabricated. One month to make and check drawings. One month for all modeling and design to be completed, and two weeks to lay out the requirements and choose the path most likely to succeed, with perhaps some very quick and dirty sanity checks thrown in there. (Modeling and design refinement continues while the components are out for fab, with phone calls and drawing revs to the suppliers to make any required course corrections.*)
He will take six and a half months to do a design. It will be beautiful, and everyone will have left the building by then.
*Some projects don't take well to course corrections, and so everything has to be right before it is sent out for fab. In those cases, with the same deadlines, more time is spent in modeling and meetings to ensure that everyone agrees that the design will meet specifications. This additional time comes out of fabrication (and maybe debug), but a phone call to the suppliers guarantees them a starting date and they can schedule the work accordingly, so your project isn't sitting in their inbox while they wrap up other work.