The USDA recommendation (I think) is like 18 months in the jars, but people say all the time that they opened a jar from many years ago and it was still good. The USDA is trying to avoid lawsuits - that's the basis of many of their ideas.

"great-grandmothers" was more of a generational thing. Neither of my grandmothers canned, but I'm sure at least one of their mothers did - though not the only one I got to meet. My mother taught me a lot of the basics, but the rest, I've had to pick up along the way - sometimes by trial and error... (some of which I'll cover in my next canning post.)

Thanks so much!