We've got a Vermont Castings WinterWarm Large insert. Maybe 10 years old. We burn only seasoned hardwood, have a full flexible stainless steel liner inside a masonry chimney that is sandwiched between the family room and the garage, catalytic combustor. We tend to burn fairly hot (too hot, have to replace some warped pieces this year). Hubby says that every time he inspect the chimney, he just sees "fluffy flyash". Skeptical me checks from below through the damper, and I feel/see/get pretty much the same thing. The only time we get gunk on the chimney cap screen is when the combustor quits - when that has happened, we also get some lightweight gunk on the ground, alerting us to replace the combustor. Anybody have similar cat stove/wood/s.s. liner - and little to no creosote? I've read through some of the forums, and it seems that this combo results in an "ungunky" chimney, but I'm a nervous Nelly, and wonder if we should clean it anyway - like now, when we need to replace the upper fireback. Appreciate any feedback!