I don't think Humphreys was quite an "associate" in the same way that someone in the East Coast Families would have been an associate, always somewhat on the outside or limited power. Humphreys was there from almost the beginning. He put in work and with the exception of a handful of people had more power than just about anyone else. When he got started the Outfit didn't have a "made man" concept.

I recommend Russo's book as well. That said, Humphreys still had to defer to Ricca/Accardo and occasionally complained about the Italians sticking together.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.