It's no secret that I'm a big fan of Ilford's Pan-F+ film. Last year I decided to answer for myself the one question that seems to dog this emulsion: is it critical that you develop it soon after exposure? In other words, will the latent image deteriorate if you don't get it processed quickly? Many people seem to believe so; it's a piece of advice you frequently hear when Pan-F is mentioned. I admit to saying so myself.
Indeed, This is what Ilford says: "Important Note: Once exposed, process PAN F Plus as soon as practical – we recommend within 3 months." Compare that to what they say in the FP-4 datasheet: "Once exposed, process FP4 Plus as soon as practical." So people give this advice, but based on what data? I'm sure Ilford has the numbers, but short of that, what does it mean for me? Are three months truly safe? What does one month look like, or six months? One way to find out: test it.
Methodology
I exposed a fresh, factory-loaded 36 exposure roll of 35mm Pan-F to the same scene at the same exposure. I then snipped a few frames and developed that film the same day. I put the remaining film in a secure location, on my darkroom shelf, keeping real-world conditions. I did another snip test two weeks later, and then at the one month, six weeks, two months, four months, eight months, and finally one-year intervals. You can see by the specific dates my breaks were not perfect. It's not always possible to get to the darkroom when one desires, but I kept it close enough.