It's only in recent years that the poor lant image stability of Pan F has been noted as a problem. It was introduced in 1951. and then as PanF Plis in 1992, I have a 1983 datashhet for PAn F and there's no mention of processing within thre months.
Agfa ceased production of APX25 in 2003 as a key compoment was no longer available, a decade leterMirko of Adox stated that they couldn't make a new version of the old EFKE 25 for a similar reason. In both cases the cost of R&D for such relatively low volume films eas uneconomic. It's quite likely that Ilford may have had to make a minor adjustment to PanF Plus at some stage.
I used some PanF Plus in my Microcord, I left a partially exposed film in the camera, and an exposed roll alongside on a shelf. When I processed the films a year later they were toast, very little omage left and mottled, completely useless.
In this respect PanF Plus is quite different to other films, normally my films are processed the same day or the next. The images I lost were not important. I'd been given the PanF and was testing the cameras Ross Xpres lens, which is actually excellent.
Ian