Lye is good for close to forever if it's stored properly in an airtight container that is not over-sized (you don't want a few pounds in the bottom of a 5 gallon bucket, for example). Essential oils, on the other hand, mostly have a relatively short shelf life (especially citrus, but others as well) and should be used within the year with some exceptions (patchouli, for example, gets better with age), and need to be stored properly (glass containers, kept cool, minimal temperature shifts)