The flying sectors are about 9-10 hours each way. About 2-3 hours on the ground at each end of the flight to turn around, add them together and you've got 24 hours.

It's probably minimum bother to leave one aircraft "captive" on 48/49 than it is to rotate it with another aircraft, if it's not necessary to do so.

There possibly isn't another 773 already sat on a gate at T5 around the same time to easily swap it, so changing the aircraft over will be a pre-meditated thing involving tugs.