From Srila Prabhupada's June 22, 1972 letter to Hamsaduta
"So especially you must encourage the students to read our books throughout the day as much as possible, and give them all good advice how to understand the books, and inspire them to study the things from every point of view. In this way, by constantly engaging our tongues in the service of the Lord, either by discussing His philosophy or by chanting Hare Krishna, the truth is that Krishna Himself will reveal Himself to us and we shall understand how to do everything properly.
Now we have got so many students and so many temples but I am fearful that if we expand too much in this way that we shall become weakened and gradually the whole thing will become lost. Just like milk. We may thin it more and more with water for cheating the customer, but in the end it will cease to be any longer milk.
Better to boil the milk now very vigorously and make it thick and sweet, that is the best process. So let us concentrate on training our devotees very thoroughly in the knowledge of Krishna Consciousness from our books, from tapes, by discussing always, and in so many ways instruct them in the right propositions."