Burn times past 8 hours?

I have a pair of butts on now that are on hour #9 and stuck at 167f. I read about 16 hour burns on a single load but I can't get past 9hrs. I've just added a few more briquettes because the temp began dropping with very little fuel remaining.

I started with a single load of Kingsford in a Kingsford chimney. Dumped the chimney on a full ring of Kingsford and assembled. The temp quickly rose to a grate temp of 230 where I held it for the last 9hrs. The top vent open full and the bottom vents open about ?. At the tail end of the 8th hour my fuel began to run out causing temps to drop below 200.

What are you guys/gals doing to get longer burn times?

Thanks.

The Minion Method calls for distributing only 15-20 hot coals over the full ring of Kingsford, then perhaps stirring the coals if the temp begins to drop at the 10-12 hour mark. You may have to add more coals at this point, although some say they regularly go beyond 12 hours. I recently went 13 hours with no problem in 50*F temps with drizzle but no wind.

Maybe the full chimney got too much charcoal ignited too quickly, cutting short your burn time?

Regards,
Chris

Chris called it right, by puting in a full chimney of burning charcoal you used a lot
of the coals up early in the burn and if you have wind, that will cut down the burn time.
Don't be afraid to add a chimney load of cold coals the ring and stir the ash a little to get it to fall out of the ring.
Jim