Odds  Inserts
----  -------
  1%  ~28e6
 10%  ~45e6
 50%  ~65e6
 90%  ~83e6
 99%  ~96e6
[download]

By those values, the odds against not having seen a duplicate by the time you reached 100 million inserts are so low as to be a pretty damn good definition of 'impossible'.

And yet, empirically, none had been seen by the time I reached 779,967,210.

And after 1.5 billion inserts, that calculation suggests that the odds of finding a value that doesn't match would be minuscule, and the "possible dups" count should be growing at almost the same rate as the new inserts are being tested.

The reality is that I've only had 1323 collisions after 1.5 billion inserts. These are the last 8:

...
1585072919
1585138596
1585355107
1585418593
1585422956
1585468018
1585558107
1585577984
[download]

They are coming much more regularly now, but they are actually still within the bounds of usability.