So.... 350 grams falling 1 meter will power this puppy for around 6 seconds. We'll err on the side of conservatism and call it 5 seconds to make the math easy. That means that if we raise the height to 2 meters we can expect the time to double to 10 seconds. If the weight is increased to 10 kg with 2 meters of travel distance I should expect somewhere in the neighborhood of 5 minutes of illumination per "charge". Not bad.... not great, but not bad.