We stock up with the large quantities of flours, rices, oatmeal, grains, etc. in January/February when the temperatures outside are below freezing, AND we leave the items in the garage for a week so that all bugs and their eggs are destroyed - they we RE-package it for use during the rest of the year.
I do things in a similar manner. Usually, I repackage and place the bags (double heavy-duty ziplocks) in the freezer for a few days. Still, they can become re-infested, from what I read, so, whenever my freezers have room to spare, I park the grains in there until I defrost/restock. This also helps freezer efficiency, as they are kept full.