Well, that would make more sense of the exactish 5 year estimate.
And that's why I think it's the case.
But I was of the impression that they would find a cure faster,
They would have found two cures, both faster than 5 years (actually in Year 2). First the false cure that probably involves using some form of shadowtech (from the Earthforce blackprojects end of things, possibly by Major Lee's group - mentioned in "End of the Line" the S1 Crusade finale.), and then the real cure found by Gideon and crew (while the Excalibur was a fugitive ship) who rejected the false cure.
just as the virus is quicker than was expected,
with some races, e.g. Dureena's people. Some races are closer to the Minbari template.
... and then become a fugitive ship.
After revealing the tradeoffs of using the false cure. Like making a deal with the Devil, you may gain something, but what did you lose?
.. What parts of this did I get right?
One does not necessarily negate the other. It could be that after a certain period of time, the virus fixates (locks onto) a race, and won't reset to the default five year clock. By the time it finds Dureena's lost tribe in "Patterns of the Soul" it's already been exposed to humans on Earth for probably six to eight months. Remember, they suspect the virus has a hive mind and communicates with itself (See "Each Night I Dream of Home."). The virus
could be using FTL relays like the Technomages use for communication across vast distances (in the Technomage trilogy). Also, if the virus is using a central computer (also mentioned in "Each Night I Dream of Home."), it does not necesarily have to have been placed on Earth. It
could be remote, and use FTL relays.