Do Christians Need to Repent After They Have Repented as New Believers the First Time?

I have heard this idea a few times now. Believers just repent once and then do not need to do so anymore. Let's just look at some verses.

First, the disciples ask Jesus how they should pray, and Jesus includes in His prayer the statement "forgive us our debts as we forgive our debtors." I'm not sure why we need to ask for forgiveness as believers since this is what repentance is. Why did the Gospel writers include this prayer by which Christians are instructed?

But if that is not convincing, how about Revelation 3:19, where Jesus is rebuking the church at Laodicea, i.e., Christians, and says, "All those I love, I rebuke and discipline. So be earnest and repent!"

Does Jesus love unbelievers? Does He discipline unbelievers? And why is He rebuking them and disciplining them? So that they repent.

John argues in 1 John 1:6-10 is clearly written to believers. In fact, the entire letter is giving qualities of true believers versus false believers. One of them is that they admit their sin and are cleansed by Christ's death as a result of it.

If we say we have fellowship with him and yet keep on walking in the darkness, we are lying and not practicing the truth. But if we walk in the light as he himself is in the light, we have fellowship with one another and the blood of Jesus his Son cleanses us from all sin. If we say we do not bear the guilt of sin, we are deceiving ourselves and the truth is not in us. But if we confess our sins, he is faithful and righteous, forgiving us our sins and cleansing us from all unrighteousness. If we say we have not sinned, we make him a liar and his word is not in us. 

But if one wants to say that this merely refers to the first time a believer repents, what will he do with 2:1-2?

My little children, I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the Righteous One, and he himself is the atoning sacrifice for our sins, and not only for our sins but also for the whole world

Who is the "anyone" here? It refers back to those John calls his "little children," i.e., those John has discipled, believers. 

In 2 Corinthians 7, Paul relates that the believers at Corinth had repented of some sins about which he had previously rebuked them.

Now I rejoice, not because you were made sad, but because you were made sad to the point of repentance. For you were made sad as God intended, so that you were not harmed in any way by us.  For sadness as intended by God produces a repentance that leads to salvation, leaving no regret, but worldly sadness brings about death. For see what this very thing, this sadness as God intended, has produced in you: what eagerness, what defense of yourselves, what indignation, what alarm, what longing, what deep concern, what punishment! In everything you have proved yourselves to be innocent in this matter. So then, even though I wrote to you, it was not on account of the one who did wrong, or on account of the one who was wronged, but to reveal to you your eagerness on our behalf before God. 
 
Why would Corinthian believers, who already repented when they believed, have to repent of their sins afterward if Christians don't need to repent anymore?

In Acts 8:13, Simon the magician becomes a believer and follows Philip wherever he goes, but after sinning, i.e., after he became a believer, Peter tells him to repent lest he perish (v. 22). 

Paul rebukes Peter to his face because by his actions he was denying the gospel, and thus "stood condemned" (Gal 2:11). 

When speaking to believers, James writes, "Draw nigh to God, and he will draw nigh to you. Cleanse your hands, ye sinners; and purify your hearts, ye double minded" (4:8).

Believers who are ensnared by the devil and oppose the leadership God has set in place should receive patience from the elders in case God should grant to them repentance (2 Tim 2:24-26). If they do not need to do so, since they already believed, why does God need to grant it?

This is not even to mention the countless calls upon God's people in the OT to repent of their sins, and we must not forget that their sins were being covered by the death of Christ just as ours are. 

As my fellow elder likes to say all of the time, We are clean, but we still need our feet washed from the dust of the world that often gets on them. Repentance is a continual practice of the Christian who wants to conform his life to Christ in all things. He is not perfect when he first comes to Christ, nor perfected afterward in this life, but he is cleaned by the blood of Christ toward perfection. Without it, he defies God and remains unclean in his sins.