Many pastors wonder if their sermons are too long. My friend Dr. Gary Miller recalls when the sermon gets near lunch time, members of the congregation lift their arms and look at their watches practicing the tradition he humorously calls the Southern Baptist salute!
Spurgeon had advice for pastors on the length of their message. He used the illustration of bread.
Do not overload a sermon with too much matter. All truth is not to be comprised in one discourse. Sermons are not to be bodies of divinity. There is such a thing as having too much to say, and saying it till hearers are sent home loathing rather than longing. An old minister walking with a young preacher, pointed to a cornfield, and observed, “Your last sermon had too much in it, and it was not clear enough, or sufficiently well-arranged; it was like that field of wheat, it contained much crude food, but none fit for use. You should make your sermons like a loaf of bread, fit for eating, and in convenient form.”
-C.H. Spurgeon, Lectures to My Students, p. 77