In other words, how many sessions does it take to make the brain changes permanent?
That really depends on your goals. Your actions are a reflection of the neural pathways in your brain. If you combine Mendi’s neurofeedback practice with a practice of a lifestyle change, you can see the effect in the ease with which your behavior changes. When you feel comfortable with whatever behavioral change you are working towards, just practicing that behavior is sufficient to maintain the neural pathways underlying it. This time frame is different for everyone.
For example, if you want to increase focus and you are combining your Mendi practice with a consistent focus task, you will know when your focus on that task becomes easier. At that point, the most effective course is to continue using Mendi and switch your focus task (for example, from uninterrupted reading to meditation). This will broaden the role of focus to more aspects of your life. After the new task becomes easier, you can continue with just a consistent practice of your lifestyle change. Brain changes can be maintained with behavioral changes.
Exercising your brain, however, can be more than just supporting one behavioral change. You may want to slow the frequency of your Mendi practice (i.e. from 3 times a week to 1) after a few months, but keeping your Mendi practice in your life will continuously benefit your brain. Your brain is plastic, and so just like the body, exercising it is a good thing. Do you stop exercising your body when you feel you’ve reached your ideal athleticism? Probably you continue exercising to maintain it. Brain changes become stronger and stronger with your Mendi practice, but the brain is plastic, and so just like the body, nothing is fully permanent. Change requires commitment, effort, patience, and maintenance.