Good morning. Welcome to SR. You will find really great support here.
I gently say that it's not very likely he can take it once a month. When you have been addicted to coke, your body's receptors are screaming for it. And since he will not stay out of the environment, that makes him even more likely to use.
Have you been to Naranon or Celebrate Recovery? You would likely get very good support there for yourself. I would say it's time to take a good long look at your own life, your needs, your wants, and the things you can do to fulfill those goals.
Keep posting, you are not alone!