How Many Botox Sessions Do You Need for Best Results?

I’m considering Botox for my frown lines, but I’m not sure how many sessions I’ll need to see good results. I’ve heard it varies, but I’d love to hear from others—what was your experience? Did you notice a difference after the first session, or did it take a few? Also, how often do you go back for touch-ups? I’m trying to plan this out and would appreciate any insights!