I have 13 1/2 inches done on the body with all of the ends woven in. The pattern suggests joining the sleeves here, but I know full well that it would end up far too short if I don't add more inches first.
The question is though ... how many more?
If this yarn didn't grow... I would add four more inches. But it does grow quite a bit. So I am currently planning on adding two more inches and give myself a rest from it and see if I end up wanting three.