Must have (40% retention – 2 to 3 weeks) The look can be maintained indefinitely with regular lash fills. When properly applied, eyelash extensions will remain in place until the natural lash on which it rests falls out. Natural lashes grow in and fall out in cycles (every 30 to 90 days). Do not be alarmed — please note that this is a perfectly normal occurrence, with or without extensions. It is normal to see a natural lash with its root attached to a lash extension when shed. Lash fills are necessary every two to four weeks in order to maintain your beautiful look.