Today, the last of those packages arrived; it was the one I sent from Narooma, almost four months ago. The package I sent a few days later from Bulimba (also by sea mail) arrived some two months earlier.
No idea why. Did they end up on different ships? Was one of the ships held hostage by pirates on its way to the Suez Canal? Or did they, on a whim, send it the other way around the world?