I will watch my females when i have a group and see if she is having trouble holding. I look at how large a female she is and has she held before? Is she being harassed alot by the others? Is she hidding all the time or out withe the others. What variant she is and any information that can help. If I know how long she held for someone else or know how long she held last time before she spit then that will give me an idea of when to strip. I have some that will go full term and others that will spit on day two. In general anything less then a day has been bad results with me and the longer the wait the less problems I have.