Crew O2
As a Captain, I will never criticize a fellow Captain's decision ending with safe operation.
However, I would have handled this deferentially;
The way I would have gone with this is to switch off the crew oxygen valve for a while to see if the leak was down stream the valve or up stream.
If you switch off the crew oxygen valve and the leak stops, then you know that the leak is down stream.
I would then continue the flight with the valve in close position , and i would brief my F/O that in case we have smoke or rapid decompression, we will FIRST switch the O2 valve on, put our oxygen masks on and continue with the memory items/QRH .
If you switch off the oxygen mask and leak continues, it means that the leak is up stream the valve, I would then calculate the rate of depletion and see if I can make the nearest suitable airport, if it appears that I will not, then , and only then , I would declare mayday and descend to MEA or 10000 feet.
Your rout off course can dictate a deferent course of action, flying over the Himalayas for instance, will force you to take escape rout maneuver into account.
In this case, they were over the Atlantic, terrain was not a factor so, I would have done what I said I will do.
This may sound scholastic but, its safe and economical at the same time.
Your thoughts please?