Since this year's wood supply is better seasoned than any in my 15 yrs of burning, my normal "Holiday" cleaning interval of Thanksgiving, Christmas and Valentines here in SE PA has been completely passed over. I haven't cleaned my stack once, although I have been keeping an eye on the flue cap, which is usually the first and best indicator of creosote buildup. But get this - today I sat down in the corner of the den, in a chair I don't use too often, and from that angle I noticed a huge red flag - the stack is sagging down from the weight of the creosote inside! Normally the EL and horizontal pipe are more or less level to the floor. I installed it - I know. But when I saw a noticeable down angle on the pipe tonite, it clued me in! At the very least I have to take off the bottom cap and dump the loose creosote. And I have a damper sealing kit which fixes the T to the upper sheet metal plate with two aluminum straps and two bolts. If I didn't have that support, the darn thing would probably be a lot worse. Always keep a critical eye on your systems!