We have a case where the client has an annual maintenance contract with a vendor for procurement of service.Payment is made on a monthly basis. We can create a Blanket PO for this. But I would like to know the significance of blanket releases. When the vendor gives a bill, we can directly make an invoice, matching against the PO.Why do we need to carry out the blanket release at all? In fact, we can have a Standard PO, and prepare PO matching invoices every month, when a bill is raised;and that should take care of the requirement.
Blankets come in handy when the vendor does NOT know the service / delivery schedule in advance. So you negotiate a long term price with the vendor in advance. And then you create releases and send them to the vendor as and when you have firm requirements. The vendor delivers the goods/services according to the date /qty on the release.
In your case, if delivery dates and qty is set in advance, you may not need a blanket. You can simply keep billing against one std. po.
Hope this answers your question