Just to prevent confusion, air is roughly 78% nitrogen, 21% oxygen, 1% 
other.  Using pure nitrogen would eliminate the 21% oxygen on the inside of 
the PVC, which might slightly slow the deflation.  It would also eliminate 
internal oxidation of the PVC, although external oxidation would still 
occur, as it was still exposed to air.  Periodic re-inflation with nitrogen 
would have to be done under more controlled conditions, not just "pucker up 
and blow."  (Yes, I know we don't want to introduce all that moisture and 
saliva!!!)

Marc

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