Unfortunately, only time will tell whether or not he will remain clean. What he does to stay clean, whether treatment, steps, etc. seems to be statistically of little consequence. People that go to AA/NA, treatment, therapists, or do none of previous seem to do equally well when it comes to staying clean/sober (or equally as bad). So, while there is no true way to tell, though you can observe old behaviors that may predict relapse, you shouldn't discount him just because he is not doing something you hear others say he "should" do . Certainly, he should make changes, but the time he has remained clean so far is a very positive thing.