I buy Linwoods Milled flaxseed. It comes in a sealed foiled packet. Once opened, It can be resealed and kept in the fridge. Before resealing it I squeeze all the air out. I open it and decant some to a tupperware type container, which I also keep in the fridge and use this. Mine has never gone off and I keep the sealed packet a long time. I think milled and ground are the same thing. Could be wrong about that. I don't use it as a thickener. I sprinkle it daily on food.