UFO, I don't want to start something. I apologise for the tosser remark even though I did call you a pilot (which you are) and not a tosser. However I can see how you would interpret it that way. I just get annoyed at what I perceive as people stirring the pot on pprune when it's supposed to be about sharing rumours and interesting gossip.
The plane is obviously airworthy otherwise why would the crew bother to write something up and ground the plane in Cloudbreak if they are already flying an unairworthy aircraft...what's one more problem hey?
My vague understanding with the A320 is that you are correct about the age and in a sense about the operators. It has only been owned however, by a few companies who controlled all the maintenance etc and then wet leased it to the others you mentioned. I can see how all those operators etc can seemingly put a tarnish on an aircraft's history. The reality is that everything is recorded that is done to an aircraft and CASA (and Skywest for that matter) would have gone through it with a fine toothed comb before letting it onto the Australian registrar.
If you are talking about aircraft ages you'll probably find the vast amount of FIFO work is done in aircraft of a similar age. Unless the bosses at RIO, FMG, BHP etc are going to start paying a lot more money this is not going to change in a hurry.