Yep, you can rebatch at any time- there's no earliest or latest point, although the earliest you get to it (when it's still fairly soft and hasn't lost most of it's moisture yet), the easier it is. If you wait until later when things are drier/harder, you may want to spritz your soap gratings with water, cover, and let sit over night before commencing to cook them. I find that doing that helps to make things go easier/faster.