RoadTired.... if you want a light for the "just in case I am riding after dark", get the S-Mini. It's light and small and has plenty of light. You won't mind carrying it with you. And the faster you go, the more light you need. You'll need 2000 lumens if you really want to go 30+ miles per hour (if that is what you consider downhill, flat out; I think you'd be crazy going that fast at night because of the dire consequences of crashing at that speed, but that's your decision).

Expensive lights have issues too. That's why I always recommend two lights for night riding. And yes, I carry an extra battery.