If every human generated one address every second their entire life, that would be 2^64. There would need to be 65536 earths before the collision chance crosses 50%.
And, in that case, it would be extremely likely that the collision would occur with an address that has never stored any bitcoins at all (meaning, that you wouldn't even know if you collided).
Remember that a MAXIMUM of LESS THAN 2
51 addresses can simultaneously hold any bitcoin value at any given moment in time.