Professional Quality - Lavish Lashes Professional Eyelash Extensions are semi-permanent eyelash extensions that can last up to 4-6 weeks depending on the life cycle of your own natural eyelashes and other factors your Lavish Lashes Professional will review with you at your first eyelash extension consultation/appointment. Though the average cycle of a single lash is about 90-120 days, factors such as your eyelash characteristics, lifestyle and general care of your eyelashes will affect how long your Lavish Lashes will last.