2 Peter 1:12, 13 (NKJV)
When I was young there were not many channels to choose from on television and there were a limited number of things you were able to watch, today there are many channels and many programming possibilities. One thing that there is more of today than there was in the past is what are known as reruns. Some show that had been previously aired was rerun, it was repeated at a later date. For me there are some shows I could watch over and over while seeing others once is more than enough. This same principle is true with the Bible, but only in the positive sense.
What Peter writes about in the first chapter of his second letter is very interesting. Peter talked of reminding people about some things, even though Peter himself acknowledges that these same people knew and in fact were already established in this truth. Despite the fact that they already knew something Peter recognized the importance of going over it more than one time. Today it seems like some people think that if you just hear something one time it is more than enough, even if they are not really established in that truth or they don't completely understand the principle involved.
To be strong, stable, effective Christians we need to be thoroughly established in the truth we find in the Bible. That means we need to hear the truth of God's Word more than once, even if we have heard it more than once before, even if we already know a lot about it. If we keep the attitude that we have more to learn it will enable us to continue to learn more while on the other hand if we think we know it all we hinder our ability to learn. We should all keep a teachable attitude towards the things of God and keep on hearing the truth, we need to hear it more often than we realize.