And it only took a month!
I was so excited at finishing bobbin #9 (that small, unfull one at the bottom right), that I wound it off into a ball and started Stage 2 plying immediately. One viewing of "Serenity" later, and I'm into bobbin #8, and have almost a full bobbin of cabled yarn. It looks a bit different from my sample, i.e. thinner and less bouncy, but I'm hoping that impression is due to 1) the yarn being under tension as it goes on to the bobbin and 2) the lack of fulling finish.
I was also interested to see that the 2-ply showed a similar, if less dramatic, color gradation as the singles:
I kind of wonder if the finished yarn will do the same, but since I plan to skein this stuff up, wash it, and stick it away in a dark corner until, oh probably October, you'll have to live in suspense for a while. Try not to let it keep you up at night.