What is the shelf life of butyric acid?

Question

and how dangerous is it when used as a rooting hormone?

Answer 1

We have 20-year-old bottles of the stuff (butanoic acid) that smell just as bad when they are opened as they originally did!
The pure acid, I am sure, has the same sort of harmful effects as pure ethanoic acid ("glacial acetic acid").
Do a search on butanoic acid, and you will come up with modern data, I am sure.