I have a Dutch West DW2500X2 wood insert it has a 1.3 cf fire box and has an effiecency rating of 64%; I just loader her up at 7:15pm with three four inch ash splits and two four inch red oak splits (shes full) laying diagonally across the three ash spilts. Im sure the fire will reach 620 degrees door temp over 1,000 degrees fire box temp. Problem is it will only give out great heat for about an hour and a half, then the temp will start to drop to 400 where it will stay for another hour or so. So i will not touch it for three hours over that shes starting her downward sprial to no heat. Is this common for a small fire box and low effieciency rating. Would I do better with a small fire box and Higher effiecency rating. I think with the load l mentioned above i should get six hours burn time and heat, they advertise this model to get eight hours of burn time; ive never ever seen that not even close. Im thinking of every reason why Im not getting the burn time but maybe its really the size im working with.