Nice rereading those passages, Mandryka. It’s been so long...
My point is that, from the viewpoint of the narrator, Swann always has the same age, from his visits to Combray when the narrator is a young boy (and even before that, in Un amour de Swann—events that take place before the narrator’s birth) through his death. And this is so for almost all characters in À la recherche... with whom the narrator has contact. Only in Le temps perdu, after the narrator has been separated from the circles he frequented, have the characters (Charlus, the Prince and new Princesse de Guermantes, the Duchesse de Guermantes..) aged significantly (in some cases, beyond recognition). This IMO is a faithful reflection of “real” life: as the age difference between us and those we frequent on a regular basis (family, friends, colleagues) is fixed, the absolute age of each one fades into the background and also becomes “fixed” (unless infirmity or sudden physical decline enter the picture).