Another thought is prediabetes, did you have a 3-5 hour Glucose Tolerance test ? with your B12 levels, what score did they class as normal ?
Rose always recommends AT LEAST 1,000mcg of Methylcobalamin, you can't have to much of it, some Neuropathy patients overseas are treated with 36,000 mcg a day, of b12 methylcobalamin.
No, there no exact time frame with this disease, for some it only stays in their feet or hands and doesn't move away, but it can move up your legs, stop at your knees and others it can go body wide.
Stress can and does aggravate PN, large amounts of sugary food can aggravate PN patients even to those that are not prediabetic or diabetic, alcohol can also aggravate the nerves.
anyway good luck,
Brian