It can really vary depending on how far you want to go with it. At the peak of usage in my youth we were all taking in excess of 30 a week, some even 30 in one

It can really vary depending on how far you want to go with it. At the peak of usage in my youth we were all taking in excess of 30 a week, some even 30 in one evening (dropping 4 each time)! Interesting things start to happen when you get that deep, such "mid-week blues". Where you just get really upset half-way through the week (the other side of the weekends), teary and somewhat irrational. Typically this is around the point where people give it up due to the side-effects. We knew we were taking too many when we uttered the words: "its tuesday, so we'll only have 6". Thankfully it isn't at all addictive so it's not hard to stop. :)