So – on the side of never enough lumens, but showing some respect to fellow citizens, pedestrians, walkers, soldiers, dogs, doggers by dousing or dipping lights.
As to the willy waving thing – more light in the right place lets you ride closer to the speed you would in the day light. If you ride by candle light you just won’t go very quickly. Unless of course you just ride slowly all the time in which case you can probably get buy with those old Ever Ready jobbies from the 1970’s.
What lights are people actually running?
Personally I run Four4th Holy Moses on the bars and a Four4th Genesis 3 spot on the helmet for plenty of light down the trail.