I have a Hearthstone Mansfield and my burn times have been going down hill for a while. When I looked in the stove I could see the cement on the joints was missing in quite a few areas, so I picked up some Rutland stove cement, cleaned the stove with a wire brush, and went to town re-sealing the joints. I thought I did a good job, guess not. Most of what I put on has come off after about a month of burning. I followed the directions on the tub of cement. Does anyone have any tips, or maybe a better brand of cement, they would like to share with me? I need to sort this out as I'm burning too much wood and the stove doesn't want to get above 425 degrees. Thanks guys.