Will masseters keep shrinking with repeated Botox? How can I maintain the effect without further slimming?

Will masseters keep shrinking with repeated Botox, or is it possible to maintain them where they are? I have TMJ and started Botox last year. Balancing pain reduction and facial slimming, I now get 25 units/side and have a little jaw/preauricular filler to fill in. I’d hate my face to get slimmer than it is after now (I’m 3 sessions in; first dose was much higher since pain was a lot). Generally, at what point does the atrophy stop and how can a person maintain the effect without more slimming?