Five lessons learned during research on a variable reflectivity, completely inorganic, thin film electrochromic window were : (i) the "rocking-chair" model is valid, and has been, and is expected to be, useful in guiding the design, development and production of the window; (ii) with appropriate processing, charge transport through the six interfaces can be managed properly; (iii) nearly complete stress-change compensation during switching can be achieved for the window; (iv) electrochromic materials of opposite carrier types are desirable; and (v) one can fabricate, routinely by a production-type process, completely inorganic EC windows which are electrically, mechanically, and optically robust.