There really is no specific time it depends on how quick they grow etc. I tend to put my animals in their adult cages quite early.
I recently got a 4-5 month female panther and put her straight in a 2x2x4 screen cage. This is bigger than they need as adults but I keep female the same as males. She has been fine. Aslong as they are getting their food they wil be fine, and they love the extra space!