In 2 Peter we are told that Peter is sensing clearly that his life is about to come to an end. This alone would give Peter a sense of focus and intentionality as to how he would spend his days and what he would devote his remaining time to doing. He says in verses 13 - 14, "I think it right, as long as I am in this body, to stir you up by way of reminder, since I know that the putting off of my body will be soon, as the Lord Jesus Christ made clear to me."
Peter also says, "Therefore I intend always to remind you of these qualities, though you know them and are established in the truth that you have." (v.12)
Let me make two observations. Peter had two good reasons to waste the remaining time that he had left doing whatever he wanted to do. First, he could have reasoned that sinse he was leaving this world that it wouldn't matter what happened after his departure. Like Hezekiah, Peter could have been glad that his life would not be consumed with the troubles that were ahead even though they would fall upon the future generation. Secondly, Peter could have believed that since these believers already knew and were established in the truth that he could not worry about them falling away or forgetting the important things.
But Peter did not believe either of those two lies. Instead he was determined that in the time he had left he intended to remind them of the truth that they needed to know. Therefore, he wrote to these churches a second letter to reinforce these important things. Perhaps it is in this that we see at least one of Peter's primary motivations to minister faithfully right up to the end. His motivation was knowing that there were only a few things that really mattered. There were only a few things that would be profitable for them to know (1:2-3). There were only a few things that contained the grace needed to give these believers everything they needed for life and godliness.
"A preacher must often be upon the same things, because the matters of necessity are few; we must not either feign necessaries, or fall much upon unneccessaries, to satisfy them that look after novelties; though we must clothe the same necessaries with frateful variety in the manner of our delivery." Puritan Richard Baxter, Pastoral Ministry
May God give me the discernment through His Word to know and be about the truly important things.