According to the experts, comfrey tincture will keep for twenty years if stored in a dark location where it can NOT evaporate. The active compound Allintion is stable, and will remain strong stored in the alcohol.

That said, My last batch lasted less than six months, I supply a lot of people including one Lady that broke her own back in a training accident. I stir up the tincture about once a month, just because; and set aside a 4 oz bottle just in case. :D