I have extended my handling time to 3 days and started using priority stickers for all large letters since 24 October.  No issues from that date yet still dealing with items that are overdue from 17 October.  Australia Post has closed my enquiry on 100 items that were well overdue (luckily most have arrived - 6 refunds - only one neutral and 4 late shipment defects - thank goodness most buyers are understranding souls).  Wrote a formal complaint to the Ombudsman about Aus Post delays but sadly not even an acknowledment back from them. 

I don't trust priority stamps anymore. I bought some small items from a seller 3hrs away from me in the same state (VIC) and they sent them in a letter the next day with a priority stamp on it. My letter then went for a lovely long trip up to NSW and back before arriving in my letterbox 3 weeks later (NSW postmarks all over it).

"Priority" no more.

Look at it this way....if you had not put the Priority sticker on it the item would probably have taken 6 weeks for it's sightseeing tour.