Descent of the brows, as one of the earliest changes associated with facial aging generally starts in the 20s. However, such changes are slow and subtle at this phase and thus most people in their 20s and even 30s are not really considered good candidates for surgical brow lift from an aging face standpoint in my opinion. The surgical lift will result in scarring of the tissue that can make future surgical attempts more challenging it also may result in un-natural or even paradoxically older appearing looks for young patients.Overall in such cases, if the anatomy is unusually favorable or the goals are really modest (for example, just trying to subtly lift the corners), chemical brow lift with neurotoxins such as Botox (being more subtle and short lasting), should probably be tried first.Of course, the cases of previous surgical scars, traumatic deformities and similar pre-existing conditions are exemptions to the general aesthetics mentioned above.