Peter teaches that we do not look at time in the same way that God does. We are finite beings, bound by time, but God is not. As a result, our perspective is naturally short-sighted, while God keeps a long-range view beyond our ability to comprehend. Remember, these verses appear in the context of Christ's return, so what the Father and the Son consider to be a short time before the Kingdom is established can seem like an eternity to us—or as if He delays His coming.
The apostle also indicates Christ's longsuffering as a reason that the end has not yet come. In our opinion, He should have returned already and put a stop to all the world's wrongs. However, His longsuffering is not due to slowness or tardiness, as the carnally-minded think. Rather, His longsuffering is a gift to us, so that we do not have to perish in His judgment.
Our focus tends to be on how bad the world is getting, yet Peter subtly draws us back to our own spiritual condition. Jesus is longsuffering toward us so that we have ample time to repent, not in the sense of initial conversion, but to turn fully and have our hearts completely changed. In its fullest sense, repentance is not complete until we are finally in His image.
Even though we may be frustrated that we do not see more end-time prophecies coming to pass, Peter explains it as a blessing to us because it means that Christ will not wrap things up before we have had a full and complete opportunity to repent. We can be thankful for God's timetable, not because it means we have more time to flirt with this world, but because He is providing everything we need to follow our salvation to its conclusion, including the time.