I recently used some old Aghfa paper from the late 60s early 70s - was fantastic! No fog at all. Round 15 Postcard recipients had their pictures printed on this.
However, I also used some early 80s Agfa paper and it was quite bad. I would agree that storage would play a big part in it's "keeping" abilities.
I just bought some Benzitriazole to ward off some slight paper fog on 20year old Ilford paper which is only just showing on some boxes and not on others.
If I could just get my hands on some more of the 70s Agfa stuff, I'd be in APUG heaven!!