Some women are under the impression that, should they discontinue using hyaluronic- or collagen-based injectables to plump their pout, their lips will deflate or sag once the filler wears off. This, however, is not true.
Fillers do not damage the existing tissue; they simply add volume by allowing the material injected to be interspersed among the fibers and cells already there. As fillers gradually disappear, lip volume returns to its previous condition, but not less voluminous.
Keep in mind that lips get a little thinner with age, so if you do volume-enhancing treatments for quite a while and then quit, you’re going to see the change that would have occurred over time.
Also consider that you may have forgotten just how thin your lips actually were before treatment.