Despite the hefty price tag, lash extensions do not last forever — but they should stick around for at least two weeks. Many technicians recommend getting a touch up every two to four weeks if you want to maintain the look. "We all have a growth cycle for our lashes, so it doesn't matter which salon you go to," Shirai says. "Everyone loses six to 20 lashes a week. When your natural lash sheds, you're going to shed the extension along with it."