I know the theory is that using plastic containers without a mylar bag will allow O2 molecules to slowly penetrate the container and allow the contents to go rancid or otherwise spoil, and maybe that's true with some types of plastics. We have been using the rectangular-type 64 oz. jugs (because they nestle better on a shelf) with an O2 absorber pack for almost 2 years now, and the O2 absorber-created vacuum has remained intact on all but one of the jugs we've opened. I think that one was a bad seal. We've stored, oatmeal, powdered milk, cornmeal, beans, rice, granola, and lots more with no problems so far. So far so good. 2 years and counting. Has anyone else tried this?