I typically let the girls spit on their own because striping can be very stressful and it will damage them for quite a while. Usually what I do is after I see the Female Labidochromis caeruleus holding for 5 days plus I isolate her.
Consequently, within 2 1/2 - 3 weeks is when they'll spit their fry depending on how comfortable they are and their environment. Afterwards, I immediately place the female back in the tank so she won't think twice about eating the babies,but most of them don't anyways.
Good luck,
RM