When I got shingles a few years ago it initially felt like an inner ear infection so I didn't seek treatment for about five days, so I was well beyond the 72 hours.
My pain subsided quickly after taking Valtrex, but I had numbness on my scalp and forehead for about three months. The doctor I saw told me that he only sees post hepatic neuralgia in the elderly, and not in anyone younger than 50.