The flue was swept before we started this season in the last week of October, similar amount of burnt tar then after the entire winter (5 months?) as I've just removed after a week under three months.
There has been a fire in it most days since the 23rd Oct from about 1500 with the last logs going in about 2100. The stove is quite large 10kW output but with a boiler rated aroud 7kW so I guess the flue gases are generally quite cool. We are burning seasoned hard wood (mostly beech but some birch and a little possibly oak), with the bark falling off and shakes opening up in the end grain. Generally it'll get through 4 x 9" long 4" sized logs every hour, so something over 15 logs/day.
Is that level of light crispy tar build up sort of expected? I don't mind digging it out every 6 weeks or so, more concerned about buildup in the flue and risk of a fire up there...