You have to remember that they could get very stressed and end up killing each other. Introductions with mice take forever and a day, so it's really best to keep everyone together until you absolutely have to separate them. It could be 3-4 months before any of those females becomes pregnant, or it could be 3 weeks. You just never really know.

It will usually take longer than a week for a female to get pregnant. They have to get used to each other and it may take more than one heat cycle for her to become pregnant at all. They go into heat every 4-5 days and she may skip a few heat cycles if she's not comfortable. She can even resorb the babies if she's stressed and doesn't feel it's a suitable environment.

With the Ball Pythons, they will be on adult mice soon if they aren't already. So really, having 3 litters within a few days of each other won't be much of a big deal. They still need to grow up a bit and gain some muscle mass after they are weaned. The males tend to grow faster than the females of the same age, so you could feed those off first, and save the females for the next week or whenever.

You could have a tub of keeper grow-out females, and when your current females are needing a rest after 3-4 consecutive litters, you can take 3 females out and replace them with 3 new females. Then your older females can have a break while the new females are getting introduced and getting pregnant. Then you could switch them back and put them with a new male.