I have a jotul castine wood stove and use it as my primary heat source.. We have been using it for about 2 and a half winters this last winter i noticed it really would heat up fast and i had a little trouble controlling the burn as it would over fire according to the temp gauge i have on top...i think that might be my fault but i am always nervous about loading it up with a lot of wood before bed. how do i know when to rebuild?