An eon is an indefinite, undefined period of time. Most rap careers are fleeting and flame out after 5-10 years, yet Jay-Z is still just as strong a name after three eons — in hip-hop’s case decades, apparently — as he was when he first hit the scene.
As far as the numerology, he probably means to divide his career into three “acts”: (1) Reasonable Doubt and the In My Lifetime… series, which established him as a “street” rapper with a golden ear for pop hits (2) Blueprint and the Black Album, in which he ascended to the pantheon of the best 3-5 rappers of all time (3) His post-“retirement” career as the world’s leading rap icon, the kind of celebrity that even your old white grandmother has heard of
Note that in Thelemic cosmology (a 20th century occult religion), mankind is currently in its “third aeon”, the Aeon of Horus. Kanye’s oversized Horus chain may be a nod at this belief system.
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