I use both those products with my adults, but I don't start the young dogs until they're over a year. I thought I remember that was what was recommended by NF.
I start my guys at around 6 months on the same product I give my seniors (it's a human one containing Glucosamine, Chondroitin, MSM, and HA), but at a lower dose.
Having had a girl with ED before, I tend to think of it as just being prophylactic - in case they develop joint issues down the road. May not help (my now 12+ year old that was started this way doesn't have issues, but maybe he wouldn't have anyway), but doesn't seem to hurt.