How frequently must you do your neurobics?
We used to say it takes 21 tries to learn a new habit. But brain exercise is something you should be doing constantly throughout the day. Try to integrate it into all of your daily activities. We have to constantly reroute activities throughout the day. But a lifelong habit of challenging the brain gives you a greater reserve of mind muscle to use. Think of it as your retirement account. Add to your 401k of the brain so you have more to draw from when you need it.
It doesn't matter how much mental exercise you do if you're on certain medications because they could cause memory issues. What about those?
The sad truth is that you can do everything right and still get Alzheimer's disease. But there are some medications which might be helping your body, but hurting your brain. It's worth finding out from your doctor if you can do without some of them, or simply take them on a short-term basis. It's best to check with your health care provider if you're on muscle relaxers, anti-spasmodics (which many older people take for spastic colon or bladder issues) or, if you take any of the older antidepressants. There are also a lot of over-the-counter medications, such as antihistamines and anti-diarrheals, that can impair mental function and shouldn't be taken long-term.