The thing about ibogaine, so I hypothesize, is that it basically makes it much easier to succeed in the (major) step of quitting heroin, etc. cold turkey. It does not make therapy/counseling unnecessary to continue the abstinence successfully. It's not a miracle, it's just a drug.
There will always be that feeling of openness, of familiarity, toward whatever substance you're coming off of. For example, I only smoked cigarettes for about four months, but even after having quit for around half a year (more than enough time for any physical side of the addiction to fade) it's still hard to resist accepting an offered smoke from a friend. Once you do something like that (smoking, opiates, whatever), you've crossed a psychological line, and it no longer seems like such a big deal, even if you loathe the thought of becoming addicted again.