Between 2001 an 2011 I cleaned my pipes 4 or 5 times. Between 2012 and 2018 I didn't clean them, and there was no difference. Being lazy in this regard I welcomed that. Then I read a post by a potentate on another forum who advocated not cleaning for the improved taste of the accumulated tars, nicotine and resins, going so far as to say that he didn't plan on cleaning his 7 Upshalls, as that was all he smoked, until such time as the draft suffered. I liked that idea too but quit before I could test it.