According to John 14:26, the apostles received the last revelation that would ever be given this side of eternity. Jesus told them

But the Counselor, the Holy Spirit, that the Father will send in My name, He is the One Who will teach you everything and remind you of everything that I told you.

It’s a good thing that God provided the Spirit to give all remaining revelation to the apostles, as well as to enable them to remember Jesus’ ministry so as to write inerrant Gospel accounts (See also John 12:16). We know that He met with them for forty days following His resurrection talking to them concerning the things that pertained to the church (Acts 1:3), but it was only after the Spirit of truth came upon them that they were given “all truth” (John 16:13), including prophetic understanding of the future. To know that they received all the truth that the church will ever have is important for many reasons, among which are the following:

1. We can be sure that claims to additional revelation are false, and know, therefore, to reject them.
2. We can know that there are no more prophecies to be forthcoming.
3. We can know that the Scriptures, in which all truth is deposited, are sufficient for our lives.
4. We can know that the more that we study the Bible and come to know the truths therein, the closer we come to knowing all the truth that God has disclosed (not that any of us gets all that far).
5. We can know that there is a source of truth available to those who ask the Spirit to enable them to access and appropriate it as they study the Bible.
6. We can know that God has completely provided a fixed rule of faith and practice for us in a world where everything else seems uncertain.

How richly God endowed us when in the coming of the Spirit, we also received all truth through the apostles!