The caveat is that the treating physician have enough experience to know the right quantity to add so as not to give you too much Botox. You won't "overdose" but have increased risk of brow ptosis if the doctor adds too much to the forehead when there is already some effective Botox in the forehead. Keep in mind that Botox doesn't last the same for all people. Most people have about a 3 month effect. Also, it doesn't fade out all at once, it's a gradual process. The fastest to go is the forehead, and the slowest to go is the glabella. Also, duration is dose dependent. I like my patients forehead to not be frozen, so they get less, but that also means that it won't last as long.