I found soap decades old, very likely older than half a century. Hundreds of boxes and hence thousands of soap bars. I'd regularly found them for years and years here and there for my great aunt had stashed those left and right. I found some in system ceilings (!), in the attic, in the basement, in drawers.

My great aunt died years and years ago (RIP) but as recently as a few weeks ago my brother and I cleaned/emptied a garage where she had hidden some stuff.

More soap bars.

I don't need the physics/chemistry: I know that soap is a stable molecule. I suspect some of the soap bars were dating back to WWII.

My great aunt was also in the "waste not / want not" camp. But as she lived through WWII as a teenager, she was in fear of ever missing things again. Hence the soap bars.