Yup, we read that before that time Sin has never entered God's holy kingdom. It is when Satan's pride, power, and jelousy of Jesus engulfed him by his own will that sin became manifest in the world.
Satan decided to separate himself from God by refusing to follow the harmony and peace of the heavens and exist within the principles of God's kingdom(which are summarized in short by the ten commandments).
Up until that point in time, angels didn't have a concept of sin. And most importantly, they didn't know the RESULTS of sin. Now, when Sin and Evil is destroyed for good and God's love will reign throughout the universe all the worlds that God created will remember the battle between God and Satan and the Great Controversy that we are a part of right now. We will all remember what the results of sin were, how much death and pain it brought upon those infected by it. And even more importantly, all the angels and God's created beings will remember the love that God himself poured out over our small world to save it from sin by sacrificing his only Son, a member of the Godhead, in order that we may be given eternal life. Through this Great Controversy all will see how God's love was manifest and how destructive sin was. They will love our Lord for what he has done and no one will even as much as think of experiencing somethings like sin.
That's why in a sense we are blessed to be here and be a part of this great battle that is going on. Think about all the worlds that were created by God already, and those that are yet to come. Out of all of them, in a million years we will be able to say "Yes, I was there in the middle of it all." We will be able to recall to others our experience during the time that we are living now, as a living testimony of God's amazing love for his created beings. We will be able to tell them just what sin did, and how relentlessly Satan fought for our souls. That's why Revelation tells us that we will be priests and councillors in God's kingdom, because of the things we went through, our obedience to God and his commandments, and the wisdom which God has given us through this ordeal.
^^ Just somethings for you to think about
Now Juneil, can you specify whether you are talking about the 1,000 years in heaven or the kingdom after sin is destroyed?