I don't think it should be an issue. Everyone getting them from Amazon is getting them without real seals, just cellophane tape all around the lid. There's no way these vendors are filling these jars with nitrogen, I would believe that as much as I believe in chem trails. This is an inert substance in normal conditions such as you would store pharmaceuticals. If you want to put a time limit to feel super safe, I would say 1 year just like Walgreens does.
OR for overachievers, get a bunch of silica gel packets and SorbiCaps/dessicants, then you can store it better than the factory did.