I was reading the ICC manual online (was not given any literature by my installer 8 or 9 years ago when the pipe was installed). They advise that one should always sweep WITHIN 48 HOURS of shutting the stove down for the season. I'm sure this is to prevent any creosote present from converting to the shiny hard to remove dangerous creosote, and suspect that this advice is reallly important to follow if you tend to get much creosote in your chimney. So, it is probably also really important for anyone with significant build up to sweep during the heating season, prior to leaving home and shutting the stove down for in excess of several days?? Wonder if the recent poster, who had shiny creosote for the first time, despite no change in burning technique, had shut his stove down for any period without sweeping. ICC also states the stovepipe/chimney is safe for continuous operation up to 1200 F, although they recommend MUCH lower flue temp for good burning technique. That 1200 F continuous fire safe temp makes me feel really good, because I think I got mine up to 1050 once. The other thing I notice about ICC chimney, is that I get NO cresote or soot anywhere except at the sliding joint of the adjustable stovepipe. ICC says their insulated pipe keeps flue temps high to minimize cresotoe deposits, and I guess it really works. I never have gotten any deposit near the cap, during 9 years of burning, and my flue (interior) is exiting into really cold temps often.