Do you only get Botox re-administered if wrinkles reappear?

At first, I thought I could just get another shot when the effect wore off.

However, I heard from those around me that there are cases where they manage it before it fully returns to normal.
I'm a bit confused about when I should go to the hospital.

I'm also worried about getting hit too often.
But I don't think it would be a good idea to wait until the wrinkles deepen again.

For those of you who get Botox regularly, what criteria do you use to schedule your appointments?