Salves can be kept for up to a year, depending on how they are stored. Storing a salve in a cool, dark place and avoiding getting water into it, will keep it fresh for longer. If you make a big batch, I recommend transferring smaller amounts into a jar that you will be opening frequently. This means, the rest of it isn’t exposed to air and potential contamination every time you use it.
Just keep checking in with your salve around the 1-year point. When it’s starting to go off, you may notice a musky smell to it as the oils start to change. This is the time to make a fresh batch!