Is the duration of Botox shorter than expected?

Lately, I feel like my jaw muscles are gradually developing, so my face looks wider in photos; I am considering getting Botox.

People around me say that once you try it, you'll want to keep getting treatments, but I'm hesitant because I've also heard that the effects last shorter than expected. In particular, since I tend to clench my teeth, I'm worried that my jaw muscles might flare up quickly. I'm curious about how long the effects of Botox usually last and whether first-timers can experience natural-looking results. I'm also wondering if chewing food feels awkward or if my cheeks look sunken after getting Botox. I would like to refer to reviews from those who are consistently receiving Botox treatments.