Will 10+ sessions of Botox to the masseter muscles eventually cause them to stay down permanently?

In my opinion the toxins do not last or render a permanent result.  I have seen some patients who get as much as 5 months and others who get a little as 3 months, which is the average expectation.  Best wishes.

Hello.  Even with many sessions of repeated Botox, the results are not permanent.  Often, the results are better with repeated treatments, but if you stop the Botox after 10+ sessions, your masseters will eventually return to their size before you started Botox.  Make sure you see a board certified physician with experience in cosmetic injectables.  Some non physicians can be good injectors, but these always work in a practice under the direct supervision of a board certified cosmetic doctor who himself/herself also is experienced in cosmetic injections.  Take care.