liquid oxygen if kept in airtight container wll last how long without vapourization?

The bp of liquid O2 is -183 °C so if your container is a regular container it will blow up even if it is a sealed metal container within a few minutes. Liquid O2 is dangerous in its own right as it explodes on contact with combustible material. We used large quantities of liquid N2 (bp -196 °C) and it was stored in a large dewar (50L). There is slow evaporation but it would last at least three days (over a long weekend). See pic at

http://en.wikipedia.org/wiki/Cryogenic_storage_dew...

we transferred the liquid N2 from the large dewar to small open-mouthed Dewars (1/2 full 1 L). You would still have about 50% after several hours.

The dewars used to cool modern supercon NMR magnets (4K) are even more efficient: refill once a week for outside liquid N2 dewar, once a month for liq helium as I recall.