Nick, I had a discussion with a detailer in a main dealer on this type of stuff, basically his view was similar to yours but he said once small scratches set into the ceramic coating which it does with time, from washing and polishing, he pointed this out on several cars that had had the treatment, then it became nigh on impossible to get a showroom shine back even using a machine buffer. In his view normal car polish care was the best option and protecting exposed areas with clear film as you say.
