This particular study used 6 hours, though I've seen others that used 12 and even 18. I think the problem was keeping a steady temp--it was supposed to be at 24C, which is 75F, but the lowest my incubator would go down to was around 90F. So I kept opening the incubator, running it off and on, in order to try to keep it around 75F. But it swung back and forth between 70F and 80F. If I ever happen to be incubating eggs and a 75-degree afternoon coincides with day 16, I may try again.I don't think your issue is with common sense.
How long did you let the eggs cool?

I may try the hour-a-day cooling cycle meant to mimic the hen leaving the nest.