Hello, all. I am an experienced hookah "barista" (shisha-rista?... Is there a terminology? Haha.), with working in the field for almost six years now and have been smoking for almost nine years. I still have troubles with explaining to my customers that I cannot continue to give them coals when I know their bowls are dead - mind you, some will try a smoke a single bowl (with a phunnel/funnel) for nearly three hours. I explain to them that there is no tobacco left to smoke and that it is not good for them nor for our equipment. The usual response is, "Well, it's already unhealthy for me so it doesn't matter.".... I don't continue to give them coals but am looking for a way to POLITELY explain to them the negative effects and how I am doing my job by trying to provide them with the best smoking experience (despite the fact that, yes, smoking isn't good for you, duh). Any advice would be much appreciated. Thank you.