Best Practices for Open Purchase Orders

Summary:

What are the best Practices for "Open" Purchase Orders in ERP Cloud

Content (please ensure you mask any confidential information):

Hi, I would like to know what are the best Practices when creating "Open" Purchase Orders in ERP Cloud, that would be created for reccuring costs and possibly an unlimited period of time.

Is the best way to create a 2 way match PO which would be in "open" status in order to be able to match an invoice against this PO, pay the invoice, and then modify the PO when it is needed (by adding quantities or new lines) and creating a new invoice of the amount of the new lines, matching the updated PO ? If the PO is linked to a BPA, is the process any different ?