Most Twichery Oils are made fresh when you order them.
Other oils, however, we call "cured," meaning that we make them in advance so all their elements have plenty of time to synthesize into one singular essence, otherwise they will not be ready when they arrive to you.
We "cure" oils when that's THE right way to do it, as some oils need WEEKS to undergo that process correctly. Based on the combinations of some herbs and their needs, it is ONLY the curing process that makes them effective in your spells.
You will know whether an oil is made fresh or "cured for maximum potency" because we will state that specifically within its listing near the end; FRESH will be in this sprightly orange text, and CURED will be in this lovely earthy green text.
Happy Spell Crafting, My Darlings!