When applied and cared for properly, eyelash extensions will last indefinitely with in-fills. Because the extension is attached to the natural hair and not the skin, there is no opportunity for damage to the natural lash growth cycle or lashes. The length of the lashes, natural eyelash life cycle and lifestyle can affect lifespan, which just means more regular in-fills are required to keep them looking full and fabulous. Like your nails and the hair on your head, your individual lashes eyelashes grow out on a continuous cycle of replenishment.