When I hear hardtack I think about sailors, pirates, scurvy, and all that.
It’s not that hard to make and it really does last. I made some about a year ago and have it stored in a jar in my pantry. Seems to be the same as when I put it there after I made it.
Cooked some Campbell’s (cheating, I know) and threw a chunk of hardtack in there about the size of two zippo lighters laid side-by-side. Ate the softening edges as they rehydrated from the soup. By the time I had finished both portions the ‘tack was softened and edible.
Remember to throw the ‘tack in ASAP (before heating if possible) so it has max time to soften. Next time I make it I will go thinner to make hydration easier. The downside is this will increase surface area and so may decrease storage life.