Why do some accounts not have any displayed Last Accessed date? I know some of them have logged in before.
It's possible, however unlikely, that they may have only ever logged in during crazy peek times when I disabled that tracking. The architecture has been changed since, such that we won't need to do that anymore, but it is possible.
It's also possible that they created their account but never actually logged in (they just visit the site, without logging in).
That's the only way that an account can be lacking a "Last Accessed Date"
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It's all in the reflexes.