MRP is designed for “just in time” planning that relies on daily job and PO generation.  Daily generation is needed because all dates in the master schedule are inter-connected in end-to-end fashion to meet required dates.  Running MRP at less than daily intervals injects late dates into the schedule that cause job release delays and late shipments.   

If your objective is to generate fewer and larger quantity jobs and POs, never attempt to accomplish this by delaying MRP generation.  Instead, use the item Supply Days setting as needed to increase the size and reduce the frequency of POs or jobs.