a long time ago, Lew Rothman wrote in his cigar almanac that you should not let you ash get long at all, he feels the cigar would take on the taste of the used ash. Robert Hacker in his ultimate cigar book, thinks one should prepare to remove the ash from the mother ship after about an inch. This sounds reasonable to me, for you don't want the cigar to burn hot, and the ash helps it stay cool. Out of a scientific curiousity I have smoked a few robustos, most notably the Puros Indios, and finished the cigar with the full ash intact! Also use common sense, if you are in a formal situation with formal clothes on, the last thing you want is for your ash to fall off on you. Me, I smoke in a gringy old moldy shirt, what do I care if the ash falls on it and catches it on fire? I feel the ash adds a nice musty texture to my "smoking shirt"
