Getting inconsistent results with the Twitter API? I found this gem in Twitter API documentation:
Lastly, there may be times in which the rate limit values that we return are inconsistent, or cases where no headers are returned at all. Perhaps memcache has been reset, or one memcache was busy so the system spoke to a different instance: the values may be inconsistent now and again. We will make a best effort to maintain consistency, but we will err toward giving an application extra calls if there is an inconsistency.
So, I’m not sure there’s a way to definitively tell if you’ve retrieved a user’s entire timeline history. Or, at least definitively determining that you’ve found their earlier tweet is complicated.