Eyelash extensions are semipermanent lashes that are hand-glued on top of your natural lashes. Unlike strip lashes, lash extensions are glued on individually to your natural hairs, so they're super customizable and actually look real.If you take care of them well, eyelash extensions can last for up to eight weeks or until they naturally fall out like lashes do. Once this happens, you can go back and have your lash technician fill in the missing pieces. So, hypothetically, you can make your extensions last indefinitely.