ebeth:
You are describing a scenario that, if they were totally honest, I think most Christians would have to admit to experiencing. It is hard to say for another person whether one did not repent, or whether it is just a struggle with the flesh. From what you said, I would say it is simply a struggle with the flesh.
When Christ died and rose again, our sin was dealt with, all of it. When we repent of our unbelief and our running from God and turn to Christ as the only sacrifice for our sins, we receive that forgiveness, but we are also born again. We pass from death to life, and are no longer sinners, but saints. This does not mean that our flesh is no longer a problem or that we will not be tempted, and it is no guarantee that we will never give in to a temptation.
I don't believe that victory over any particular sin "has" to take longer than any other, but in reality that seem to be the way it works. We are being changed, being transformed.
I came from a very performance oriented and very typical pentecostal background. If I ever sinned after I was born again, I beat myself up for weeks. Funny, it was never the little things that I was "convicted" about, but only the big besetting things that were repeated. I finally came to the place of realization that if I felt "convicted" over some big repeat thing but never did feel the same about getting angry with someone unjustly or about selfishness or self-centeredness in some area, that this "conviction" was in reality only condemnation stemming from myself or from the enemy. Don't get me wrong. I am not saying that God does not convict me of things that He desires to change in me. He does this all the time. But He does not beat me up for a week over one mistake and ignore the deeper and greater issues in my life. His conviction causes me to run to Him for forgiveness, not feel worthless for weeks.
What I came to realize is that all sins are equal in the sight of God. All sins are unequal in the eyes of man, and have varying degrees of consequence, but sin was dealt with on the cross. Notice sins and sin. Actions that miss the mark, and sin. There is a difference.
I learned to rely on the mercy and grace of God, to realize that He does not need to shed blood again for every infraction. I respond in obedience to the Holy Spirit when He speaks to me. I agree, "Yes Lord, I blew it again. I rely on Your forgiveness. I accept it right now." This is easy. The hard part is forgiving myself and moving on.
Then I am obedient to whatever He tells me to do about the situation.
Ultimately, I find that giving in to temptation and lack of victory over the flesh is inversely proportional to my love relationship with Him. The closer I walk to Him, the less I have problems with overcoming the flesh. If I become a bit "distanced" from God, I find myself having a much harder time with the flesh.
Hope that helps
Travis.
Oh, by the way, I just read Friedrick's response. I need to make a disclaimer:
The fact that this person (me) has stepped up to the plate to attempt to answer this question does not imply that this person is a giant, knows a giant, has ever met a giant, nor has he played a giant on TV. :-)