An interesting question. Of course the model sets emulsion fog as a constant. This is in contrast to developer fog which increases with development. If the film is exposed to create an image and the film is not developed the activation sites (latent specks) will migrate about destroying the image and resulting in an overall increase in fog. This is ensured by the Second Law of Thermodynamics. But this would take a long time. The time would be shortened by higher temperatures. This is why exposed film should be kept cool before development.