I think you're right about the 70's. After Giancana was deposed there were a succession of bosses, but they didn't last very long. There were no longer any qualified members who met the qualifications. Accardo would step in just long enough to handle things until a new boss took over.
In all fairness, it should be noted that the govt. stepped up their efforts to nail every boss who "came on board." Times changed and there was an obvious lack of talent to assume the role of boss.
