I can say from experience that I have developed Pan F 6 months after the images were taken and got superb results. On the other hand, last month I found a roll of exposed Pan F that contained pictures made over a period of time from 14 months prior to 6 months prior. That roll had serious problems. This didn't make sense to me since some of the images were only 6 months old and I had previously been successful at developing Pan F that old. What I don't know is how fresh that roll of film was when the pictures were taken. It's possible that it was near or past the use date on the box.

Dave