I have a 22 foot high 2 foot square exterior brick chimney with a 7 and 1/4 inch square terracotta liner, and that is lined with a 6 inch stainless liner and poured insulation.
I have one 90 degree elbow into the thimble.
So I figured right now would be a good time to experiment. I had a bed of coals, maybe an inch, or two, the coal bed was below the air inlet dogbox. I loaded 7 pieces of oak, split 2 years ago in March, so it sat outside taking the summer sun and wind for 2 years. In fact this particular wood received direct sunlight all afternoon and prevailing winds for two years. (I know it will burn much better next season, which is I when I will be using the bulk of it)
The stove top temperature was 200 degrees and falling, outside temp around 22 degrees under high pressure.
I loaded at 8:10 pm, air wide open
8:35 and the stove top temp has dropped to 160 degrees.
The fire is just starting to go. It sat there with very small flames licking around under the front split. I then opened the side door to re-count how many splits I put in and indeed it is seven. At this point the upper splits erupted in flame.
8:40 and still no secondary burn though the front splits are burning. The stovetop temp is closing in on 200 degrees. It's been a half hour and still no secondaries.
8:45, flames becoming more vigorous, still no secondaries, stovetop temp not quite 250 degrees
8:50, telltale sounds of the cast iron heating up, you know, the clickin and tickin... can distinctly hear the air sucking into the stove... 280 degrees on stovetop, no secondaries yet
8:53, stovetop temp is 325 degrees, secondaries starting to kick in
9:00, stovetop temp is 425 degrees, full secondary action.
9:02 stovetop temp is 500 degrees.
There, that took 52 minutes to do that. So, maybe you all would like to do the same some time and post here. I think the main difference in time it takes to reach 500 degrees is draft/chimney setup, however, barometric pressure/wood type etc. may also change the dynamic.
edit to say at 9:10, fully one hour after loading, the stovetop temp is at 600 degrees, air was wide open the whole hour, time to throttle down!