Since a machine must be threaded with paper or film support, and the entire track or alley, as we called it, can be up to a mile long, rethreading a machine and getting it up to speed takes a master roll and then some of support which cannot be used. Therefore each shutdown can use more than a blank master roll.
In addition, for uniformity, all products are blends of ingredients from the previous batch. No product that I worked on was the result of a single run, but rather was a blend of a blend of a blend going back to the first run of that particular emulsion.
BTW, it seems like you are agreeing 100% with you, right? Not that I mind, but I did get a laugh out of it.