That is just about time for a round trip to Wellington, New Zealand. Would the extra leag have a positive or negative effect on the economics of the Sydney route?
FWIW up until the mid-nineties BA operated a significant number of "tag on" services out of SYD (e.g. AKL, MEL, ADL) using the 747.
AFAIK ( i.e what I was told at the time) the reason it stopped ties with what Max Tow has said - the economics didn't stack up.