I've had it said to me that once you see a porn image it's stuck in your head for life and I feel like there is some truth to that idea. Sexual images are very compelling.

In that sense someone who's seen pornography may never eliminate it from their life... since the memory is ever ready to leap to the fore when one is so inclined.

If by "eliminated" you mean stoped looking up new material... again I question the reality of such a goal. One may never see a photo or pic or video of two people engaging sexually but as males are visually stimulated... even a kid taking his shirt off at the beach can be a pornographic moment if we let it. I'm confident that there's no eliminating our sexual imaginations.

I'm wondering what's behind your question really.
If the issue is that someone is struggling with a compulsion towards certain behaviours... like looking at internet porn... and one is feeling powerless to stop doing so then can I again recomend Gerald May's book, "Addiction and Grace". It has to be the most comprehensive and helpful book on dealing with such behaviours that I've read.

Freedom is available. Even if you feel powerless to overcome... there is a way out.

Blessings
Cat.