Approximately 2-4 weeks if you respect your new lashes and take care of them. Remember this is a semi-permanent beauty procedure. A real lash’s life cycle is around 25-28 days, and as yours grow and fall out, so will the synthetic ones that are attached. If your hair and nails grow quickly then that may indicate that your lashes also are growing, shedding and renewing themselves quickly so you may find that your lashes will not last as long as someone whose hair growth is slow. Your lifestyle will also make a difference how long they last.