Every time I hear these arguments I just think "buy gold" (or other precious metals) and be done with it. It weighs a lot but I feel its value will never really diminish, even in a post apocalyptic setting. At some point someone will trade for rare shiny metal that has practical uses beyond just being rare and shiny (e.g. anti corrosion coatings.) Whereas government issued money might be useful as toilet paper and crypto a distant memory of failed technological promises.