@deerafl
I don't know it would work much if it's split between 5 peoples. Probably for the mothers.
This is my theory, I apologize if my explanation is not clear (and I'm kinda bad at math too).
How I see the curse work is, if it takes a full day, it would be like as if it was a permanent curse (like a repeat of the curse once it's midnight making it as if it was infinite).
Splitting three differents full-time curse into 3 will reduce the curse time (24 hours divide divide by 3 peoples = 8 hours each).
The curse splitted between the mothers would be 12 hours for each (must be hard for the mother who has the curse between midnight and midday but since it is also possible to take the curse time with the one you shared the Happy Prince...).
About each curse:
Shirayuki and her mom has the sleepiness curse (2 peoples x 24 hours)
Kuromori and her mom has the cat transformation (same as above)
Suzuki has the machine curse (24 hours solo)
The curse machine splitted between 5 would have lasted 4,8 hours.
My guess for those who has the same curse, it would adds up, so I'm guessing it would make 48 hours
Splitting a 48 hours between 5 would make a 9,6 hours of cat transformation and sleepiness, making it almost 2 hours more than before. It won't be easy to have a correct school life IMO.
It would have been better if they had different kind of curse each so it won't last too long.
But then again, that's just my theory.