My symptoms have also been very slow and gradual. They have their own periodicity too - I have weeks where i feel great, then WHAM, the symptoms come back. This seems to be closely tied to my stress levels and my sleep patterns. As for the progression, it's very hard to say. I think the general tendency is that if the cause of the PN is overlooked/missed and not treated, it will progress. Be sure to have your vitamin levels checked -b12, e, etc