After all the evidence was in. And there is evidence OTHER THAN reporters' testimony, that implicates Libby in a lie.
This seems important to me since it was clear at a very early stage that Plame had been stationed in the U.S. for over 5 years and was not covered by the applicable law.
The resolution of that underlying matter is irrelevant to the question of whether or not Libby lied.
This would be a fact easily discovered by Fitzgerald and the investigation should have been over at that point.
Without Libby's lie, assuming there aren't other liars involved, the case is over. Without the lies to the GJ, there would be no bill, because 50 USC 421 et seq were not violated.
What if that lie was in month 15 and it was known that there was no crime because of the 5 year rule in month 2 wouldn't you question the motives of the prosecutor in keeping up the investigation?
That is why I'm interested in the timeline.