Sorry, didn't mean to be misleading, $75 is not a fee for unlimited cleaning, I meant it as the minimum amount, because she will go as long as she is physically able in a day to get a house clean, as she only cleans one house a day. There has been only one house that she just was not able to complete in a day.
If the job takes her more than one 6 hour day of hard full-time cleaning (because I think everyone that has had her clean sees that she is cleaning for every minute that she's there) and she needs to return on another day to finish, then it seems only fair that it would be an additional fee, as it is additional work.
If you have a large house, or multiple pets and children, the best idea may be for her to come see the place first and let you know if she thinks it's going to take longer than one day, so that you both have an idea of what's expected.
Sorry for any miscommunication!
Sylvia