Quote Originally Posted by Chamaeleo View Post
I have never heard of this problem either in UK. In the past I have developed Pan F and other Ilford films several years after exposure, even ones kept in a camera in the tropics, without any apparent effect. Where is the original evidence on this perceived need to keep the time between exposure and development as short as possible? I would like to know because I might learn something new.
From another recent thread about PanF (emphasis mine):

Quote Originally Posted by bvy View Post
I promised to follow up. Allow me to sing the praises of Ilford.

I sent the bad film to Ilford for inspection. Within about two weeks, I got a detailed response via e-mail from a technician. She checked the batch number of the film and found no other complaints or anything unusual in the coating/finishing records. She found nothing unusual in my development or storage of the film. As such, her findings were inconclusive. She did admit that "latent image regression" was the one weakness of Pan F Plus, whereby films developed more than six months after exposure could potentially come out slightly faint -- but, she said, not nearly to the degree that I've experienced. Even so, she could only guess that it was an extremely rare case of this phenomenon, and, as she put it, "that you've been extremely unlucky." She and Ilford were very generous in replacing the film.

I've since had good luck, together and separately, with both Pan F Plus and Perceptol. In fact, I'm considering Perceptol (stock) as my developer of choice for Neopan 100 Acros, of which I have a lot on hand.

Thanks to Simon and to Ilford for their excellent customer service and standing behind their products.
I've seen this as well with PanF, and have lost shots to films left undeveloped for a long time. I once ran a test and shot half a roll, stored it for four months then shot the remainder. The first half was noticeably thinner upon development. A month is not the end of the world, I myself wouldn't go longer than that without adding development time.