I've learnt a painful lesson, cutting a 100g skein of yarn in half does not equal two balls of the same yardage. I knitted on yarn over cable sock doing 39 repeats of the 4rw pattern from the heel and cast off. I knit the second to 36 repeats of the 4rw pattern and didn't have enough to cast off. I attempted to spit splice with the small amount of yarn left from the other sock but it didn't work, perhaps because the yarn is superwash. So then I tried a knot and kept knitting and it looked ugly. So I gave up and undid both, ended up with 33 repeats of the 4rw pattern which are still lovely long socks and actually fit better too.
& So I am left with a nub of yarn. Now I used to think that avoiding this was the whole point of knitting from the toe up. However the stress of trying to get equally long right to the last tiny bit of yarn socks is just too much. Next time I should just pick a length, know I'll end up with two nubs of yarn. Pick something from 653 patterns to knit with 1-285 yards and have fun. Long live the nubs.