Yummi W cd attach>detach>attach lesss than 6 sec early game.

first of all yuumis w cooldown begins on first cast.(basically like a riven q) and the static cd goes from 10 to 5 to 0. now i'm not sure if yuumis w is effected by cdr if it is then she's basically double dipping cdr.(but i can't find anything about that on her league wiki) anyways all you need to know is that yuumi's w has effectively no real cooldown.