How do you usually schedule your Botox injections when your jaw muscles feel stiff?

I have a bad habit of unconsciously clenching my teeth while sleeping, so when I wake up in the morning, the muscles on both sides of my jaw are always stiff and tight. I was also stressed because my face shape seemed to be getting more and more square, so,

I heard that Botox is the fastest and most effective way to loosen stiff muscles, so I'm thinking of getting it for the first time in my life. I heard that since it isn't permanent, I need to keep getting regular treatments to keep my jawline slim.

I am wondering if it is generally best to visit the clinic when my muscles start to stiffen again after my first Botox injection, or if it is better to set a fixed interval and visit regularly as a preventative measure. I would also like to hear some tips from experts on whether it is okay to extend the interval between Botox injections a bit if I use a pure toxin that does not cause resistance.