I do most of my winter riding in the dark. If not too cold I ride 3-4 times a week. Leave the house at 5:30. Ride 1 hr. about 18 miles and home again. I'm using 2 NiteStick batteries. 15w of lights. Each battery lasts about 45 minutes using all 15w. If I ride longer I will run just the 10w. Giving me just over an hour of light per battery. Two tail lights. I also have 2 other riders so we look like a small train going down the road.