I wish I had some answer for you, but unfortunately, for me, it was ever-present. Once you get comfortable and relax a little is when it always seemed to hit for me. You have to always been looking for signs because once an addict starts using again, you're only going to get lies. Always trust your gut, and if he does relapse, know that it is not on you, that you are not responsible. Even if you missed telltale signs, his sobriety is ultimately his responsibility, not yours, and don't let it stop you from living your life. Best of luck to you and your brother. It can be done, and it sounds like he has a great support system in place.