How long do eyelash extensions last? Lash extensions are semi-permanent. With the proper application and no lash adhesive, your lashes are to shed within 4-6 weeks. Lack or proper application and other adhesives may cause lashes to fall off sooner. Each person will differ based on personal care and body chemistry. If you are hard on your eyes, such as rubbing from allergies, picking at lashes, and/or using skin care products and makeup removers, this may cause your lashes to shed sooner. Proper after care instructions will be given at the end of the video.