Originally Posted by
number_6
Presumably you arrive at domestic terminal at SYD; bus to international terminal leaves every 20 min (10 at peak times) and takes 10 min. Walk in terminal is 5 min at each end. Worst case 40 min for the inter-terminal transfer.
That is not worst case. During peak morning periods buses fill up and some people have to wait for the next one. However, for dom->int at that hour not too likely unless the PER redeye arrived late.