While looking at your beauty product rotation, you can probably point out a select few that are so good, they can be hard to say goodbye to once you hit the bottom of the bottle. When it comes to the Shop TODAY team’s favorite items in skin care, makeup and hair, they make sure to use every last drop — before immediately running out to repurchase more. These are what we call our beauty “empties.” “Empties,” of course, refers to the state of the bottle once all of the product is gone. A trend popularized on social media by beauty influencers, sharing empties is a way to spotlight a beauty…