This also varies and it's mostly up to you! You don't need it before you have wrinkles to hide, or you can use it preventatively. “To be clear, it is much more about anatomy (as a result of genetic and environmental factors) than it is about a stereotypical age at which to begin". “Prevention is the new mantra, [but] I have seen women in [their] 40s with few or no wrinkles who require very little [Botox], and women in their 20s who require more.” Basically, a patient can have Botox safely whenever they are bothered by their wrinkles or simply want to prevent them from forming in the first place. There is no issue with long-term use, either: "I've had patients who have used it repeatedly for over 20 years without bad effects," says Kane. Source: allure.com