From Commbank comes the following:
" To reduce the risk of chargebacks caused by cardholder disputes, it’s important to have complete and up-to-date transaction records. A transaction can be disputed up to 120 days from the date of the transaction or the delivery date, whichever is later, so we recommend keeping your transaction records for at least six months."
So 120 days from payment or delivery, whichever is the later. Perhaps they vary the time by card type eg Gold Card, Platinum, or normal? There is some discussion re the 30 days in that a request after this time may impact the ability to get the money back, so sooner rather than later.
Also of interest is the following about the acquiring Merchant/s and/or Bank/s:
“acquiring banks and merchants have a set time limit of 45 days to respond to each phase”