Let me start by saying this is my opinion and may not work for everyone and I am a guy.
I am so tired of seeing people say they need formula for their infant. My wife nursed our children and so have generations upon generations of other women. Why stock formula, your wife has the ability to make all the food your child will ever need and it won't cost anything and you don't have to store it.
Let us what if for one minute...
S has HTF, "your" wife gets pregnant, "you" have no formula stored because "your" child is now 5 and all that "you" did have was bartered off or went bad, there are no formula manufactureres and "you" don't own a milk producing animal and can't barter for milk from one.... what are "you" going to do then?
God forbid something happens to the mother...she is separated from her baby for some reason, her milk dries up...stress and illness, not eating right and just mother nature can cause that to happen...there is the option of freeze dried milk...with Karo syrup and vitamins added if you want... cheaper than storing formula. We all drank that when we were babies...especially over 6 months. In a very bad SHTF hopefully you could find a wet nurse.