My farmer friends tell me that the reason to freeze all wheat flour is
to kill the bug eggs that are an unavoidable part of the flour you
purchase. Flour that has not been frozen and which is stored for a
long time doesn't "get" bugs, but rather hatches the little bug eggs
that are already in the flour from the start. Freezing kills the eggs
so they never hatch. [Of course, you can also attract bugs from
outside the flour, depending upon storage method, and whole wheat flour
can go rancid.]