Here is a good, encouraging word from Spurgeon on the task of preaching and the inexhaustible richness of the Word of God.
“After preaching the gospel for forty years, and after printing the sermons I have preached for more than six-and-thirty years, reaching now to the number of 2,200 in weekly succession, I am fairly entitled to speak about the fullness and richness of the Bible, as a preacher’s book. Brethren, it is inexhaustible. No question about freshness will arise if we keep closely to the text of the sacred volume. There can be no difficulty as to finding themes totally distinct from those we have handled before; the variety is as infinite as the fullness. A long life will only suffice us to skirt the shores of this great continent of light. In the forty years of my own ministry I have only touched the hem of the garment of divine truth; but what virtue has flowed out of it! The Word is like its Author, infinite, immeasurable, without end. If you were ordained to be a preacher throughout eternity, you would have before you a theme equal to everlasting demands.”