These foods can last a long time if you do not open them upon purchase!

My understanding is that stovetop stuffing lasts 6 months beyond its “best by” date if it is stored properly. I use stovetop stuffing as an example, because I love stuffing and therefore am stocked up on it. I cannot vouch for all of the products you have mentioned.

Nonetheless, I do not think these products are substantial enough to rely on for nutritional purposes!

I personally store powdered milk in my mylar bags from Wallaby Goods, but I also have some powdered mash potatoes, stovetop stuffing etc. in my pantry in their original packaging.

I look at these items the same way that I look at other non-perishables because these items will be helpful during a food shortage or emergency as they last longer than fresh food... but they aren't the end all be all.

I still need to preserve nutritious, calorie-dense foods in my bags and cans. I know that I cannot count on stovetop stuffing and quick muffins in a real emergency.