Not sure about that, I would be very surprised if the time of day effected fuel burn. My understanding is that QF107/108, QF15/16 and QF93/94 are timed the way they are so they can meet the JFK flight, but QF12 doesn't meet this anyway so I don't see too many issues with retiming it. In fact, QF would be the only airline running a US-AUS service as a daytime flight and it would provide customers with a greater flexibility as there are two LAX-SYD flights daily anyway, but currently the schedules almost mirror each other.