my understanding is that if your case is assigned to an officer, and if the officer finds out that your finger prints have expired, the officer will request another set of finger prints.
there is no such thing as automatic finger prints once the first set expire. however, you could also send an enquiry to CSC. by sending an enquiry to csc, you are forcing the ins to take a look at your case and might be you could receive the request for second finger prints.