Summerthyme, the vines had not died back but were starting to yellow at the center of the plants. I knew they might not be quite what they could be, but I was certainly expecting a little more than the nothing I got from them. The vines were gorgeous. I think the dirt was packed too hard.
I would have left them until a frost had they been outdoors, but I had 36 kale plants that were outgrowing their six packs and needed planting. I had to dig out some dirt as I was adding newer better dirt so it was a matter of time. And the kale is more important to me than sweet potatoes, which I loathe...these would have been for the chickens and maybe the rabbits had they done well. Good to know about the slips being "clones". I'd sort of thought this would be the case, but wasn't sure. I always buy two or more sweet potatoes in the fall so I will have them for spring if SHTF before then and I can't get them any more.
There are still two sweet potato plants in outdoor containers to dig. I'm waiting for a frost and for a long enough break in the rain so I'm not digging in mud. These are in big containers so I'm not worried about them rotting but I hate harvesting any root crops when the ground isn't fairly dry.