Hey Stoneley,
I have also had my file sent to PSA recently. As VS said, the time taken for them to send you a letter of invitation depends on how high they rank you.
My enlistment coordinator said that I would probably hear from the PSA before she did, so I suggest you call the RAAF switchboard on 1300 333 362 and ask them to connect you to PSA where you can ask them how your file is doing.
Hopefully see you and VS at Tamworth soon!