As recommended by USDA. I wouldn't risk anything else.
The shepherd's pie was excellent, the meat was tender and well-flavored. I'll probably try again, really packing it in this time (using wide-mouth pints). All I can think that I might have done wrong, is I probably rushed the exhausting of the jars (bringing the contents up to 170 degrees). I had the temp too high to begin with. But that shouldn't have caused this problem.
I can always freeze it, but the freezer is all-the-way full. I'm trying to find things that don't use the freezer. And it's nice to come home when work ran really late (not unusual in the veterinary world) and not have to figure out what to make that doesn't require thawing. A pint of homemade soup and some heated bread takes maybe 15 minutes and tastes like a planned meal instead of an emergency. Or red beans and rice, when I have leftover rice in the fridge. Heat, chop up green onions, get out the Tabasco and put it on plates.
There's never enough time, except on the weekends I don't work. I have to plan ahead.