If you were waiting to upgrade from ASA 8.4(5), because you would lose bidirectional flow exports, then wait no more. Cisco ASA NetFlow Bidirectional support has been added in version 9.1(2).
flow-export active-refresh interval
Did you recently upgrade your Cisco ASA and run into flow-export active refresh-interval problems? If you were starting to appreciate the numerous NetFlow Security Event Logging (NSEL) enhancements available in the Cisco ASA 8.4(5) NetFlow export you may be left disappointed after upgrading the ASA to version 8.5(1), 8.6(1), 8.7(1), 9.0(1), or 9.1(1). What happened?