I actually talked with one of the salesguys from a lightstick vendor. The way he put it was "all the sticks of the same size and color put out the same amount of TOTAL light, it's just a matter of how LONG they put that amount of light over"

AKA a 5 minute stick (and yeah they are made) is going to be about 12x brighter than a 1 hour stick, which will be 6x brighter than a 6 hour stick