Hi Jennifer,
You will have to schedule FPDUDC regularly as a batch job.
You may put the Due date value as per your requirement. Consider, you want to post those standing requests today which will be due in next 2 days, you will have to give Consider Due Dates Until as system date + 2 days.
In the general selection, you may provide the list of all BPs. So that the request line items will be posted on all such eligible customers' account everyday.
In that way, you will have the customer's account with such standing requests posted on different date with their own posting date and due date.
Thanks
Bodhisattwa