I can only speak from my own experience. Each time I was using I was able to keep things together for few months -ie- function in a career that was very stressful and required a fair degree of intellectual ability - but then something would always happen that would make me lose it, such as an arrest or getting black mailed - which is when I would get into recovery. Over time the consequences of using became worse for me. The same thing will probably happen with him but maybe try not to focus on him. I really encourage you to try Al-Anon or Nar-Anon. I know, easy for me to say, but my ex-wife died of alcoholism. When we were married (which was before my drug use) I would try everthing to stop her from drinking - she was literally killing herself since she had late stage liver disease. Her drinking was absolutely driving me insane. Al-Anon helped me so much then - I think I would have lost my mind without it.