In the recent past there have been groundings of the F-111 fleet due to corrosion problems with the wings. The RAAF bought a large number of surplus wings from the USAF years ago, and has enough to last for at least for another few years if the aircraft do not sustain heavy flight times. Some of the F-111's have even seen avionics updates to improve delivery of new weapons systems.
There is possible gap in the in-service date of the F-35 and the retirement of the F-111, but as long the RAAF keeps working hard keeping the Aardvark in the air we'll see F-111's in the air for years to come.