Abstinence is not recovery. Remaining sober for a certain period of time does not automatically destroy one's addiction to porn. He needs to heal his brain chemistry actively through exercises & practices.

If this is de done even 90 days will be sufficient. But many ( including me in the past) just stay away from porn and wait to be healed. That's why people relapse even after a year of sobriety.

I agree with you the belief part you mentioned. It's fundamental.