One frequently overlooked benefit of consistent Bible exposition is that the preacher’s faith and practice is tested by every text. Over the long haul, everything I have ever taught has had to survive the scrutiny of the Scriptures. By God’s grace, I’ve been able to teach through every verse of the New Testament (using the Old Testament for support and examples). Both my doctrine and my life have been radically shaped by the Word of God, as they have had to stand the test of every single text.
In the big picture, preaching verse by verse, book by book brings a divine balance to ministry. It keeps the preacher from leaving things out or from getting on a hobby horse and riding it to death. It forces him to deal with topics he might not naturally be drawn to if not for the fact that the next verse he is preaching addresses them. Put simply, it requires him to teach God’s truth in the way God revealed it. And that’s the best way to teach.
Some preachers allow their audience to determine what topic they will address. As one popular pastor has written:
Adapt your style to fit your audience. . . . The ground we have in common with unbelievers is not the Bible, but our common needs, hurts, and interests as human beings. You cannot start with a text, expecting the unchurched to be fascinated by it. You must first capture their attention, and then move them to the truth of God’s Word. By starting with a topic that interests the unchurched and then showing what the Bible says about it, you can grab their attention, disarm prejudices, and create an interest in the Bible that wasn’t there before. Rick Warren, The Purpose Driven Church (Grand Rapids: Zondervan, 1995), 294–95.
But such a bait-and-switch approach is really just a recipe for compromise—tempting pastors to tickle the ears of their audience or water down the gospel in an effort to be more appealing. In essence, this approach says that God’s Word is irrelevant, and makes human ingenuity the key to getting sinners interested in the gospel. It is therefore an approach that should be categorically rejected. As James Heidinger writes:
Evangelical pastors and theologians can learn from the mainline experience of placing relevance above truth. We must avoid the lure of novelty and soft sell, which, we are told, will make it easier for moderns to believe. Methods may change, but never the message. . . . We are called to be faithful stewards of a great and reliable theological heritage. We have truths to affirm and errors to avoid. We must not try to make these truths more appealing or user friendly by watering them down. We must guard against a trendy “theological bungee jumping” that merely entertains the watching crowd.  James V. Heidinger II, "Toxic Pluralism," Christianity Today 37/ 4 (April 5, 1993): 16–17.
We are called to preach the Bible consistently and accurately, fixed on the text as the revealed Word of God which, through the work of the Spirit, alone has the power to save and sanctify souls. When we do this, we can be confident that God is pleased, since our preaching will be in keeping with His Word (cf. 2 Timothy 2:15; 4:2).