You'll probably need to provide some more information to get the answer you want to hear. But, while I haven't put anything into a secondary fermenter, I believe you may be referring to a conditioning stage either in the primary or in a secondary fermenter. If so, this is really a "clean up" stage of the process. I don't go by time so much as looking to see it clear and the yeast drop.
Maybe describe your whole process and the specifics of the recipe and those with way more knowledge and experience than me will give you a more direct answer.