I think that the NT recipe suggests that you start tasting it after four days. If it is already that vinegary, you might want to go less than ten days next time. It depends on the weather and all kinds of other factors, so testing it is a good idea, at least for the first few batches. It is still good for you, so you can just drink small amounts, or leave it in the fridge and mix a bit of it in your cup with the next batch, or my favorite idea would be to use it as starter, because the more vinegary it is, the better it protects against mold, etc. Also, you can just leave it without a scoby in it, and allow it to go another month or two, and the new scoby that grows will be really great (some website calls it brewing a master race scoby). I don't particularly either mind or like vinegary kombucha, but mostly use it medicinally anyway. Good luck!