You only need to store away enough to buy yourself time to adapt to the new reality. The human body has wonderful mechanisms to adapt. (And of course to buy enough time for all the zombies to devour one another)
The real question is: "how long will it take for the zombies to run their course if SHTF?" I'm guessing weeks for the vast majority of those who go feral. Perhaps the most successful/violent/aggressive of the zombies might last up to 2 or 3 months, but I find it hard to imagine that any would last longer. They may find protein in targeting emaciated urban survivors, but even in the suburbs they will find too little to eat and too little fuel to get far from the cities across roads full of abandoned vehicles. I expect barter to resume as a risky option within months, and barter with organized markets within a year, probably sooner.
“”You only need to store away enough to buy yourself time to adapt to the new reality””
That could be forever. At my age, at least until the end of my life....I can’t see the supplies lasting as we won’t recover from an EMP..no matter what or how much we stock....