The longevity will vary based on how well they are taken care of, a few natural factors like oily skin or sweat,  how well they are applied and the quality of products used. If you’re seeing a certified eyelash technician, especially one with years of experience, there is a very good chance that your extensions will last the longest that they can. Probably the most important thing to ensure your extensions last as long as possible is how clean your natural lashes are when they are being applied. If there is any makeup or oil on them at all it can get in the way of the glue bond. Making sure that all your makeup is removed and your lashes are clean gives your technician the best base for a better glue bond. A technician will usually either wash or prime your natural lashes before they start as well but it’s better if they are already clean. The other most important thing to ensure longevity is keeping them clean afterwards by using a specially formulated lash wash once a day. By using lash wash properly with either your fingers or a washing brush (or an eyeshadow blending brush) you get rid of any dirt, oil, makeup or sweat that may break down the glue faster. Overall, clean lashes are happy lashes!