You are only allowed 4000 mg of acetometaphine per 24 hours and
if he was taking 10/500 or 10/325 and
taking them ten times a day then is getting a lot of Tylenol. This over time maxing out the limit will wear on the liver. Also, with a tolerance that high, will most likely have a pretty rough first detox. I would definitely recomend saying something to them and try to convince them to get help. A habbit like that is either expensive, deadly, and or torture to loved ones around him.