Actors take one show at a time - it's hard to show up at more than one rehearsal. Lighting designers overlap shows, but, again, can only show up at one Tech at a time. Costume designers, since much of their work is done outside the theater, are more able to almoooost be in two places at once. Set designers have the further advantages that their design and time-consuming drawing/modeling are done early and that shop and stage visits must be done when actors won't be inconvenienced ("are out of the way" is the other way to phrase that!). Tech is less important since by then the set ought to be on course - plus, it just doesn't take all day Saturday to see that light leaks through that flat or that the floor squeaks. So we can overlap shows.
Since we can, we do. Fees are low. If you need income, you need to take as many shows as you can handle. But this means weeks like this one, with meetings and deadlines on four different, over-lapping shows.
Two deadlines down, two to go.