There isn't long-term research to support Botox (or similar neuromodulators such as Dysport) in younger patients to prevent wrinkles when they are much older.
As various plastic surgeons & dermatologist have already stated, there are better methods to improve your skin and help reduce further facial aging for the long-term. While Botox Cosmetic may be used for younger patients in their 20's, you may find better results with skin care, chemical peel, or microdermabrasion first. Lastly, the general skin guide below is better than any plastic surgery or Botox for wrinkles prevention. Best of luck. - Dr. Chaboki
sun protection
adequate sleep
avoid smoking
adequate hydration
balanced diet, with fresh fruits & vegetables
regular exercise