To maintain the appearance of your eyelash extensions, we recommend scheduling a lash fill appointment within three weeks of the initial application. This is because the bond between your natural lashes and the extensions weakens over time due to oil and other impurities, causing the extensions to fall out. After three weeks, it's likely that a significant number of extensions will be lost, making it necessary to apply a new full set to maintain the desired look. We do not offer lash fill services for lashes applied by other technicians due to potential differences in lash quality.