This Low-Carb Bake Mix Information is worthy of a revisit, I think. Also this one: Flour, flour, flour - what to use instead in our baking.
Needing to introduce more fiber into your diet?: Some Bake Mix with Fiber Compositions.
See the container in the photo above? That is what I use to keep my bake mixes in. Not only is it airtight and keeps the bake mix fresh at room temperature for several months (for longer storage yet - freeze), it is also a useful container for combining the bake mix ingredients very well - simply replace lid and shake container vigorously for a minute or so. It is much more efficient than simply stirring the bake mix ingredients together.