Blanket Orders? (Magento)

Has anyone done anything with Blanket Orders via eCommerce?

if this helps, "A blanket sales order is a long-term agreement between a seller and a customer. A blanket order is typically made when a customer has committed to purchasing large quantities that are to be delivered in several smaller shipments over a certain period of time. "

Looking to offer this service, with self serve portal, via Magento… TIA.