There's really merit to both sides of the argument. I agree with Cat_5 holding his shot for now. There's still the rest of this day, and let's say Coolrock does come back, what if he happens to be a doctor type?
But there is the possibility of an inactive scum which gives the other scum greater leeway. Can't really read a scum team if they never have to interact and the present scum member can use their ability(ies) every night without having to be the one to do the NK.