How many births do you typically take on per month in order to manage your time with family, vacations, free time, etc?

For my first year, getting started, I was aiming for one per month to balance my family time and with my two-year-old to see how he adjusted to the separation. Now after one year I am aiming for two per month. It seems like doulas I know take a month off here and there so they can have a break from being on call 24/7 all the time!

Because I am a full-time student and also have a regular part-time job (as needed) I only do births during winter and summer breaks. I always try to schedule them according with my daughter. I also encapsulate placentas and take on as many as I can, for they do not take much time.