I have Thursdays off. I have one specific family of 2 that doesn't need Thursday care, and I had every other kindy kids that didn't need every other Thursday. So after the kindy kids left I just decided to not be available to anyone on Thursdays. I have missed out on clients that needed 5 days a week and I am in a smaller community so it took about a year to fill 2 empty spots.
I will again have two empty spots in September after a year of being full, and I am fully aware that it may be difficult to find new kids that can go somewhere else on Thursdays, but I'm prepared for that.
Once the family that doesn't need Thursday care is done with daycare (their youngest is just turning two) I think I will switch to being closed on Fridays. That's a while off yet, so we'll see how it keeps going for me as far as finding clients who can manage the 4 days a week.