Like @WayneSchulz we bundle SERV access agreements with all new system sales and won't adopt an orphan or ROR transfer without one. Today, we only bill annually but once we finish the contract component of our Acumatica implementation, we plan to offer monthly payment plans so long as the customer signs up for auto-payment via ACH or Credit Card.
This link with take you to the page on our site that details our SERV offering options. http://www.cs3tech.com/serv.html