30 hours on LOW, 14 hours on MEDIUM, 7 hours on MAX.
IMPORTANT - MAX doesn't mean biggest flames! If you want to have nice campfire feel with big flames, you actually want the system on the LOW setting: that allows the flames to extend and dance around. MAX setting intensifies the fire by increasing airflow and the effect is that the flames essentially collapse on themselves, creating a furnace-like effect. This is ideal for kickstarting an initial fire (see what we did there) or if you're in really chilly conditions and you're looking to radiate a lot of heat.