Regarding long audit times: It is usually best to distribute both transports (drives) and tapes equally across LSMs to minimize this effect, as well as for performance reasons. 

Tapes will eventually end up closer to their drives anyway following dismount operations if the default "Float" behaviour is not turned off, but that takes a long time to achieve.

Regarding the speedup if in maintenance mode, per the ACSLS ICAG: "The difference between online and diagnostic states is: an audit in

diagnostic state can only be performed through the cmd_proc. Client

requests are rejected while the LSM is in the diagnostic state. This state is

faster because the audit now has exclusive run of the library without

competing mount/dismount requests that could otherwise be submitted

from the client."

Scripting/Automating ACSLS commands (like "move") is also possible.