A friend once told me of a preacher he knew who had retired because he "ran out of things to talk about."
"Unto me, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles the unsearchable riches of Christ" (Ephesians 3:8).
Declaring himself to be the least among us, the Apostle Paul proclaimed his view of the riches of Christ as beyond fathoming and comprehension. The notion that one could run out of discussion material regarding so infinitely vast a person as the Lord Jesus speaks not to the limits of the subject, but of the communicator. Even more, it speaks to the aforementioned preacher's failure to access the dynamic whereby Paul and all faithful teachers and preachers discover and communicate an unsearchable Christ, namely, "this grace given."
Those who would speak of Christ and for Christ must first be supplicants of His grace. An ongoing illumination of God's unexpected and undeserved favor provided in the Lord Jesus keeps the communicator's heart continually and freshly alive with wonder. I personally do not read or listen to anyone who fails to give evidence of personal amazement regarding our Lord's completely unmerited goodness so beautifully described in the hymnwriter's joyful exclamation, "Out of His infinite riches in Jesus, He giveth and giveth and giveth again." At least in the attitude of the heart, the preacher should crawl to his pulpit in utter amazement that God should call him to speak even one word for the glory of the Lord Jesus. "This grace given" must form and fill his message. But even more, it must form and fill his heart.
Upon such a glorious basis, the communicator of the Gospel will never "run out of things to talk about." He will rather perhaps feel a sense of frustration. "There's so much to say about the Lord Jesus and His glorious person and work! Where to begin?!" Only the Holy Spirit can answer that question as He leads and guides His preachers and teachers to pick out particular jewels from God's treasure chest of Truth. Suffice it to say that no preacher ever retires from His calling. At some point he may be physically or mentally unable to continue, and sadly, he can disqualify himself from ministry (I Corinthians 9:27). The fire that burns in his heart will never be extinguished, however, nor will the bright and ineffable Light that "shineth more and more unto the perfect day" (Proverbs 4:18).
In the knowing, accessing, experiencing and communicating the Lord Jesus, it matters not how far we've come. The journey's just begun. Run out of things to talk about in this lifetime? Never! We rather run out of time to talk about them! Indeed, a long eternity will not suffice in fully apprehended the glory of our Savior's person and work on our behalf...
"O the depth of the riches both of the wisdom and knowledge of God! How unsearchable are His judgments, and His ways past finding out!"
"The gifts and calling of God are without repentance."