Wind down the air and these are sure to stay in overnight. Bark briquettes have extremely long burning time up to 10-16 hours. That is not to say you can come down next morning, give them a poke and they burst into flames, rather that there is still a good warmth in the stove and a glow from the ashes. Bark does produce extra ash, more ash creates a bigger heat store, but also more ash to dispose of the next day