Sorry, I may be in the minority on this but hoarding diapers just seems evil to me. And diapers are also incredibly bulky and one can easily go through 10 a day. You're not going to be traveling with this vast quantity of disposable wealth. (I'm just going to assume you don't have kids.)

We survived as a species for a few hundred thousand years without modern diapers. I suspect most people would rediscover the "joys" of cloth or that potty training would gain a new incentive.

Fortunately, places like CostCo allow those who can afford them to stock up on huge quantities of diapers these days.

And if water/toilet services are interrupted, cities are going to become very nasty places very quickly...
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"When I read about the evils of drinking, I gave up reading." Henny Youngman