You need to just keep going and see. I had uber sensitive teeth (could not drink anything acidic at all), and it wasn't too long that the sensitivity went away. I've been OPing for years now, and stopped once for a month, and darn if it didn't come back again. So, as it appears OP does not reverse and cure, but it seems to stave off. An on going relief of symptoms and it does keep your gums from falling apart. You sort of have to think of it like brushing your teeth.
Sometimes when all the other stuff melts off your teeth, you are left with the underlying stains and such. Coconut Oil (to me) is really good for this. But it's a heavy duty oil. Have heard of waaayyy more intense OPing stories with that oil. But really is high up there as one of the best.
I think that some peoples teeth absorb a lot of color. Might be some sort of enamel issue? I don't have all the answers, but an interesting question.