I'm a 24yo F with a very expressive forehead/brow area (raising my eyebrows creates about 5 lines across my forehead). I got 20 units Botox for the first time about a year and a half ago (Dec. '11), saw results after only 3 days and had long-lasting, spectacular results. I went to a different doctor near the end of April for the same amount in the same area, and after nearly 3 weeks, I have no results whatsoever. I called the doctor, who didn't follow up with me the week after my appointment as promised, and she now wants me to come in and pay for another 20 units because, according to her, you have to get injections every 3-4 months in order for Botox to work and the reason why I don't have any results now is because I waited a year and a half to have the procedure done again. I'm not buying it. Is what the doc said true?