Well, by now they have been emptied and partially re-filled. I also found out that my estimate of how much needs to be spun was a considerable amount lower than the final estimate is, after doing a test weave sample. It's the Law of Reconstructions and Reproductions, it seems, that if one mis-estimates anything, it's always a mis-estimate towards lower, quicker, easier, or cheaper than it turns out to be in the end.
Soon there will be a stack of skeins large enough that it will be time to draw a hot bath for them, and give them their settling soak. I've marked every skein with its number in the spinning sequence, so I can label them once they are dried - with the length in metres, the weight and grist. That will hopefully help to see how consistent the yarn is.
I'm also thinking about doing at least a partly re-skeining after washing and drying the yarn, to see if there's shrinkage. If so, I'd need to adjust the amount of yarn spun so it doesn't run out before the fabric is finished...