Recently I have been asked questions about the advisability of storing cake or pancake mixes and other similar items. My advice is not to, for several reasons. Now first I am talking about the cake or pancake mixes, you purchase at your local grocery store, not the canned products produced by reputable long-term food companies.
One reason is that you have no control of what goes into the mixes. Many of them contain oils of different types, dairy and who knows what else. The labels on the packages often don’t give you enough information for you to make an intelligent decision about storing these products. Because it is a mixture, the shelf life is determined by the ingredient with the shortest shelf life. This in the case of oils it can be as short as a few months.
Even packed in Mylar packs with oxygen absorbers, your shelf live may not be the best. I prefer to store the ingredients to make cake or pancake mixes separately. If something goes wrong with one of the ingredients, you can still make something from the remaining ingredients.
I have read articles about people getting sick from these products being used well after their expiration date. Now I have not been able to find any hard fact on this, but suspect it was from improper storage that allowed mold to form.
Another problem that I have read about is people saying that the baking powder loses it strength. I have not been able to verify this, but have found information that baking powder stored by itself will store for many years. Here is a link to a post that I did a couple of years ago that reference a study done by BYU on the shelf life of baking powder. The shelf life may be shorter when it is mixed with other products.
My advice is if you want cakes and pancake store the ingredients separately packaged for long-term storage. Besides homemade baked goods, taste better than the store bought cake or pancake mixes.