Our sermons are never to be just one theme from scripture painted with just different stories each week.  Paul said that we are to preach the whole counsel of God to the people that they might benefit from all the truth.  Paul gave them the basics by evangelizing them with preaching the Kingdom of God.  The church would need be fed in order to grow and to be nourished so he gave them the whole thing, the whole counsel of God.  He also warned them and gave them words of grace to build them up and nurture their growth.