Hello Dann, what sort of shaking or sliding mechanism does your stove have for the grate under the fire? What you describe is your coal burning properly untill the firepot is full of just ash, and the ash is not being shaken out of the firepot into the ashpan below.. All coal burning stoves need a way to shake or agitate the base of the fire to get the coal ash to fall through the holes and slots in the grates and into the ash pan..
If your stove does NOT have a slider, or shaker grate, then the only way you will be able to keep a coal fire going is to go under the grate, and using a poker, go through the holes or slots in the grate and get the ash to fall through into the ashpan area.. the level of the fire will drop as the ash falls into the ashpan,, then you can add more fresh coal onto the top of the fire.
The normal process is to shake the fire, add fresh coal, then 6, 8 or 12 hours later, [this depends on the stove, burn rate and other factors] shake again, and add more coal.. With a good shaking mechanism, and shaking technique and good coal,, you can start the fire once in the fall, and let it go out in the spring.
Read some of the other posts on the hand feed forum about other stoves not burning long enough, hot enough, the burning of anthracite coal is pretty universal, with minor variations for stove design, chimney capabilities and burn rate .