Well, I bought 4 qrts of GC and what I did was to squeeze the bottle until almost all the air is out and then tighten the cap. That would minimize condensation inside the bottle and ensure the cap is tight, since so many bottles come very lose from the factory.
As for oil shelf life, there have been a few UOAs of oils that are more than a year old, INSIDE a motor which definitely does not help and TBN still looked excellent. I say well sealed bottle in a dry place out of sunlight will last many many years.
Rick