How often I guess is more of a "use" question, but for the last 3 years for me I try to run the brush down the pipe this week since I have this week off. Seems to work out starting in mid October that it needs cleaned by now. Last year I had the flakes falling down the pipe sound before now. Maybe I'm better prepared, burning better quality wood this year - thanks to all here . Heard the first flakes this past weekend, and I've been keeping my eye on the cap, no black "Icicles". So since it's going to be around 50 degrees today and rain and cold on the horizon today I'll be on the roof with the ol' brush. How about y'all? How often do you clean the chimney/pipe? Mines single wall, about 12' with 2-22 degree bends