|The outer shell on the grains protects the grain. Once the shell is broken to make flour the nutrients start to degrade
Vacuum sealed flour is good for 5 years if stored at 70º F. Unfortunately heat and high humidity results in weevil or insect eggs.
When you buy a large bag of flour, I recommend to freeze the flour for 2 days. This will kill all the weevil or insect eggs. Select the jars of the size to hold a supply of flour for one week. This will reduce the amount of flour exposed to humidity and heat everyday. Transfer the flour to jars to the top so that there is no room for air. Put a bay leaf in the flour jar to help protect against insects. Bay leaves are natural insect repellents. Tightly secure the jars with lids. Put the jars in cool and dry place.
Whole grain flour has another problem, it contains natural oils, and the flour can turn rancid at room temperature quickly. The whole grain flour should always be stored in air tight container in the refrigerator or freezer.