I have ridden the last 30 rainy miles of a double century with just that light (other light drained the batteries quicker than I had thought) and had o problems. In terms of a light that is dependable I have put the cateye el-500 through some pretty nasty rainy rides that have destroyed other lights and I find it extremely dependable and very frugal on battery consumption. For higher speeds I would use 2 and usually do (second light is a Planet Bike super spot, not as water resistant but also good on batteries).