Good observation Bob. I have recently started paying attention to how much ash comes down with each shakedown. It certainly is a big clue to an ash buildup even when there are no dead spots. I have been burning coal for just under a year and am still learning a lot from this forum and from my own observations and trial and error. I think this is a big part of the joy of burning coal.
My daughter says I am a coal nerd.
I say I can live with that