Until the next time you change that particular crew member.
Think of the figure as a different firefighter who takes over while the original one takes a (hopefully) well earned rest.
We think of it as the same firefighter who just grabbed different equipment. That's why it eats up so many action points - he is taking his old stuff on and putting on something new. I don't think there is a "bench" of firefighters sitting on the sideline waiting to be put in the game!