In last years Malaysian report it says that the crew O2 system could supply O2 for one person for 27hrs at 36000ft. Malaysian Airlines had 2 bottles, serviced to 1800psi fitted, whereas most airlines just have one.
But personally, I think the crew bottle is the root cause for 370 going missing. It is the best/only mechanical failure scenario that could explain how it went missing. A bottle rupture could potentially cause— decompression, extensive electrical failures, crew incapacitation,autopilot/autothrottle failure all in an instant. The pilots made the first turn but never accomplished the emergency descent before becoming hypoxic.
Hope you find this info useful in your pub discussions!