I'm a newbie to the pellet world and I recently installed a lennox montage. The manufacturer says 15-37 hours with a full 50lb hopper. Last week when the temps dropped around here in the 20's I had to run the stove full bore to keep up which I expected but I'm lucky if I get 10 hours on a full hopper. Does this seem right? I'm burn American fiber premium pellets which seems to be a decent pellet.So do they rate the burn times on the low or medium setting?