My daughter and I tried it out. A ¼" sliver off the mushroom she has in the picture lasted about 1 mile or 15 min, so 3 mushrooms will move a spark for about a day; however it catches a spark so easily, I would just star new at each camp sight. It does not work if the mushroom is wet or too moist, dead black rotting ones work best. It also would be a great hand warmer on winter.