An estimate which requires installment payments over 12 months is possible but each month the user is required to generate a one time invoice from the Estimate UI. (You can also link from a new invoice to the previously created Estimate.) If the payment period is set to a known duration it would save time to create one "linked" invoice from an Estimate and convert the created invoice into a recurring invoice but still retain the "linked" status between invoice and estimate. Currently new invoices must be manually matched. Understand that there will be corner cases related to customers paying more than the invoice amount and a recurring invoices near the end of the recurring cycle might not have "Estimate" amount left. Would like to see the current notice permit the link between recurring invoices and estimates but warn the user if the Estimate does not have at least the value of the recurring invoice left, then the recurring invoice cycle will terminate. An option to pick that the last invoice take any remaining Estimate amount would be ideal.