On the skill reveal it states:
However, casting the skill again ends the current wave after a short time
Does increased duration extend that short time after you recast so you get more of that "waves of multiple out at once" when you cast in rapid succession, effectively giving you a longer range at which you can cast in quick succession?
Nope, there is a fixed time (I think 0.2 seconds or so) before the wave fades when replaced.