I have a vc dw2500 insert. The firebox it not real large, about 1.5 cu i think. After burning about 8-10 hrs I get a large amount of red hot coals. Gets to the point where they almost are up against the door. Should I just open the damper and let them burn down a bit?? Any help would be appreciated. I hate when my fire gets too low. (pyro i think )