Oxygen systems are designed in the way you suggest Dairyground. The bottles are lifed and also subjected to regular inspections, being removed from the aircraft and subjected to non-destructive examination and proof testing. It would be very unusual for a bottle to "explode" in service, though it is not completely unknown. As one poster has revealed, the QF "Longreach" configuration includes a customer selectable option for supplementary oxygen bottles. These would be to permit operation on routes where terrain prevents the aircraft from immediately descending to 10,000 feet in the event of de-pressurisation. It seems that this option installs supplementary oxygen bottles mounted in the location where the hull rupture occured.
Placed under deliberate pressure, a poster whom I presume to be a QF management pilot has revealed that the event was not as routine as first appears (such incidents seldom proceed exactly as rehearsed in the simulator) and that the crew had additional un-stated system problems to handle. Perhaps an oxygen system problem is included among these?