Some place I read that milled specialty grains (or maybe just roasted grains) start to loose flavors faster than milled base grains. It makes some sense to me. They are more like a roasted coffee. I think in general, if something has a stronger smell that is a sign that there a volatiles that are being lost. I suspect that milled grain in a reasonably air tight container will last for quite a while.Does the type of grain make a difference?