Before long, the oxygen absorbers will have absorbed all the oxygen they can. Obviously, your product won't be oxygen free under these circumstances. Walton Feed gets around this problem with their plastic Super Pail buckets by purging the product first with nitrogen before tossing in the two oxygen absorber packets. This way the absorbers have little or no oxygen to absorb and don't create a vacuum within the pail. As cans work well under a partial vacuum, purging them with nitrogen isn't necessary before inserting the oxygen absorber packet and sealing the lid.
Large seeds store better in nitrogen.
On the other hand, small seeds, like many garden seeds store better in air. For this reason Walton cans their garden seed packs in air. Whatever container you use, be sure it is food grade as your product can be tainted with whatever the container is made from. Plastic sacks are not good air tight containers, for even if they are sealed, the relatively thin plastic 'breathes,' allowing air to pass through. Paper sacks are of course even worse.