I don't think there's any "concern" about the edge markings. They're just a marker for the known poor latent image stability of Pan F+. The film keeps fine in the sense that you can expose it up to (and in practice after) expiration date and still get fine image results, as long as you process promptly. But if you don't process promptly the image begins to fade. The edge mark fading just confirms that, since they are exposed into the film at Ilford. This doesn't hurt anything, unless you really need those edge marks for some reason.
Originally Posted by wblynch