When you create a blanket purchase order, you have the option to setup the purchase orders manually or at lead time. You also have the ability to choose to autogenerate a schedule (weekly, monthly, etc) or do a manual schedule.  If you setup manual and put in dates where you think you might need it, can you have the supply plan generate actual need dates?  If we create dates at creation of blanket PO, the dates can and likely will change depending upon need.  For example, I have a Blanket PO, with the following dates;

8/1/2020

10/1/2020

12/1/2020

When we run the supply plan, we will see in the blanket PO suggestions to create these PO's on all three of these dates.  We will also see real suggestions (these are time phased items) on the time phased screen.  The date on the time phased may say 7/15 because our need has moved up and 8/1 is going to be late.