I can't speak to the colour paper at all, but I'm still getting use out of all of the papers you've listed, bar the Kodak Polycontrast. Storage conditions seem to be more of an issue than age, although the earlier versions of Multigrade/Variable contrast papers have never seemed to hold up all that well (I'm talking Ilford Multigrade I, II and III here).
I do a quick age-fog test with all of my new-old papers. Just a couple of two inch strips or whatever. One goes through the entire Developer, Stop and Fix process. One is Fix only. I tape the results to the box. Then I can see at a glance whether I'm going to want to break out the benzotriazole.
I also usually make a quick print with a known 'technically correct' negative, just to see if there's any contrast loss. II've made one quick attempt at adding Sodium Carbonate to the developer to increase contrast, but I ran my test on very old Argenta Metallic Copper paper - NOT a good choice when one simply wants to know the efficacy of an altered chemical formula. I really couldn't tell if it had helped or not.
At any rate, enjoy your treasures there. The Ektalure and Ilfobrom papers both worked really well for me and I've always had especially good luck with old Agfa-Gevaert. My Grade 5 Agfa Brovira is beautiful!