Brethren, weigh your sermons. Do not retail them by the yard, but deal them out by the pound. Set no store by the quantity of words which you utter, but strive to be esteemed for the quality of your matter. It is foolish to be lavish in words and niggardly in truth. -C.H. Spurgeon, Lectures to My Students, p. 71
There is no intrinsic value in an overlong sermon. Nor is there anything to boast about that a congregation has become conditioned to endure them. What constitutes a long sermon is a relative term anyway, isn’t it? In any case, a long-winded preacher is just as capable of wispy words as a short-winded one. Likewise, a short sermon is just as capable of filling a room with hot air as is a long one. Twenty minutes of gospel power would do far more for a congregation than forty minutes of gospel lite. Likewise, forty minutes of Biblical exhortation would hold the attention of God’s people far more than twenty minutes of pointless patter.
Sometimes congregations expect preachers to keep it short, and those congregations need to be conditioned over time to allow longer expositions. But sometimes preachers value sermon length as an end in itself, and they may need to measure their sermons more by the pound than by the yard.
A final word from Spurgeon:
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