Hugh,
First, let me share a little background. I spent 20 years in the industrial labeling area, putting labels on everything from small engines to processed food.
This experience has given me a critical eye on the expiration dates printed on consumer packaging. I can tell you that the production people, the ones sweating on the packaging lines, are very concerned about the safety of what they are working on. Most of them consider the dates they have to put on the cans, jars, boxes, et cetera as a joke. They know that the packaging they are sending down the line is good for decades.
With apologies to the bulk packaging/home canning advertisers, I feel you just cannot, in a home kitchen setting, match the quality of an industrial kitchen run by professionals. Is it “over cooked?” Maybe, but it is safe. (If you are canning home grown stuff, go for it! I grew up on that kind of thing.)