Well there was almost enough yarn to finish the sleeves; they were coming out somewhere between ¾ and bracelet length. However, they were also too open. I wanted the fit a bit closer, especially in the lower arm.
I'll stop right here and admit I hadn't done any maths the first time around. I just started knitting and then decided to decrease every 12th round. It wasn't enough. So much for saving time by winging it. Now I've done the maths, and I'll make decreases every fourth row. Bonus: more decreases means fewer stitches, means the yarn should go a bit further and the sleeves longer. We shall see. Whatever happens, my plan all along called for the cuffs to be dark blue.