What size cooker/firebox?
A big stick burner that eats logs will need more air space than a small charcoal burner. Also depends on how often you're willing/able to clean the ash out. I have to "sweep" my NBBD about 3 times during an all-day cook like a 12 hour brisket. My grate sits about 3-4 inches from the firebox floor; but I've also cooked without a grate and with it raised about 5-6 inches depending on the length of cook, size of fuel and heat of fire I want, etc.
More confused yet?
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