After completing the thermal mass bench fill, my stove had a whole summer in which to naturally air dry, in a 45% RH environment. By the time Fall arrived, all the brick mortar and
cob (3.5:1, masons sand to fire-clay) appeared totally white in color and dry to the touch. Even so, it took several days of daily firing before the stove stopped making condensate, and then another full week of daily firing to be dry enough so that the mass (6 inches thick) would come up to temperature normally.
So keep the stove going and give it a few weeks of daily firing, of something like 2 hour sessions or longer. When it's fully dried, you'll notice a sizable performance increase in the amount of radiant heat from the mass.