Since all those good friends are already believers, why would God have to be patient with them and giving them more time to repent? Have you considered that?
No, of course not.
Yes, of course I considered it. First, is it your opinion that believers no longer need to repent?
But to answer your question, because as believers/friends wait, we should be maturing from infants into mature Christ-like friends.
2 Peter 3:14 (LEB) Therefore, dear friends, because you are waiting for these things, make every effort to be found at peace, spotless and unblemished in him.
And how are good friends, believers, yet new born infant children of God, found to be at peace, spotless and unblemished as we temporarily wait on Him, drawing nearer and nearer? Umm, we repent of our sins.
1 Peter 2:1-4 ... 11 (LEB) Therefore, ridding yourselves of all malice and all deceit and hypocrisy and envy and all slander, like newborn infants long for the unadulterated spiritual milk, so that by it you may grow up to salvation, if you have tasted that the Lord is kind, to whom you are drawing near, ... 11 Dear friends, I urge you as foreigners and temporary residents to abstain from fleshly desires which wage war against your soul, maintaining your good conduct among the Gentiles, so that in the things in which they slander you as evildoers, by seeing your good deeds they may glorify God on the day of visitation.
25 For you were going astray like sheep, but you have turned back now to the shepherd and guardian of your souls.
BTW: Who is the guardian of our souls?
Notice the patience that Peter says God had toward the eight He saved in Noah's day:
1 Peter 3:20 (LEB) the patience of God waited in the days of Noah, while an ark was being constructed, in which a few—that is, eight souls—were rescued through water. 21 And also, corresponding to this, baptism now saves you, not the removal of dirt from the flesh, but an appeal to God for a good conscience through the resurrection of Jesus Christ,