How long does the effect of jaw Botox last?

I'm worried that the muscles under my ears look prominent and my face looks wide and square, so I'm thinking about getting jaw Botox.
Perhaps because I usually like chewy foods and have a habit of grinding or clenching my teeth while sleeping, I felt like the muscles around my jaw joint were particularly developed.
I shared my concerns with my friends, and they strongly recommended that I get Botox injections to make my face look much slimmer without bone-shaving surgery, so I am considering taking this opportunity to get them.
However, since this is my very first time getting Botox, I am writing this post to find out exactly about the benefits and duration of the effects before visiting the clinic.
I heard that the biggest advantage of Botox is that the procedure takes only a few minutes, causes absolutely no disruption to daily life, and softens the facial lines.
Aside from the aesthetic benefit of making the face look smaller as the muscles shrink, I am curious if there are definite functional benefits in relieving jaw pain or stiffness caused by habits like teeth clenching or grinding, like mine.
I would also like to know how long the effects of jaw Botox usually last.
It varies from person to person, but usually, how long does the effect last after one injection?
Also, I am wondering how often I need to get injections cumulatively over several months to maintain a slim jawline effectively.