Most of the oils offered will never change. Oils may change on occasion though, or vary slightly between batches.
When applying any fragrance please consider that there are several factors which can affect the natural smell of your skin and, in turn, the way a scent smells on you. For instance, your mood, stress level, age, body chemistry, diet, and current medications may all alter the scents you wear. Similarly, factors such as dry or oily skin can even affect the amount of time a fragrance will last after being applied.