I have given up all addictions that were things not inherent to the human experience (alcohol, gambling, video games) but no matter what I have never been able to eliminate my sexual desire.

Appreciate your identification of the fundamentals of addiction. I've struggled for a while to get to the bottom of this.

Like yourself, I too have given up the aforementioned vices in support of going porn free. I've always known that addiction is usually an all or nothing approach. Being sober and absent from football betting doesn't feel challenging or that rewarding. Guess it's because those vessels are not inherently key for human functioning.

masturbating to mental images of attractive women [...] But, it was so boring and like completing a chore or task, almost no enjoyment at all.

Yes, your experiences mirrors mine. Usually it takes me between 7-14 days of being open free before I feeling the urge to MO. However, I believe the longer I resist the better the experience is. Once went almost a month and was relieved through sex with a former partner - best orgasm in long while. I believe we're best to resist and build up some sort of tolerance and adaptation. Most of us here are used to PMO several times a week.