To be succinct, TTB requires monthly reports to be filed beginning with the month that your Basic Permit is issued. For example, if your Basic Permit is effective March 31st, you must file monthly reports for March and for all succeeding months that your permit is active. You must also begin filing excise tax returns by the required due date. If you are an annual filer, your excise tax return would be due by January 14, 2020 for the period January 1 through December 31, 2019.
To respond to your original question: I am retired from TTB's National Revenue Center (NRC) and I know that to a sometimes large degree that your amendment's processing time (including terminating a bond) depends on which NRC specialist is working it. Contact me with any questions. Langdon Guenther