Please let me know the Botox injection schedule.

Hello. Recently, I have started noticing deep, fine expression lines around my eyes and between my eyebrows. They look fine when I have a neutral expression, but if I frown or smile even slightly, the lines become very pronounced, making me look older than my age. I feel like I should start taking preventative measures before it's too late. How often should I schedule my Botox injections to ensure the muscles don't sag and maintain firmness? I am asking this question because I heard scary stories about how getting injections too frequently can lead to resistance and render the treatment completely ineffective later on. I am seeking advice from Botox experts on approximately how long the paralyzing effect lasts after a single injection, and what is a safe interval of weeks or months to maintain consistent, uninterrupted regular Botox treatments.