Robert Comsol wrote:
Now that really takes some time. I'd find it hard to believe that subspace technology had gotten worse.
However, Tal's information could be wrong and Starfleet somehow made the Romulans believe that it would take that long. Kirk doesn't comment on the time a reply would take.
Or Tal and the Enterprise are not in the same location of space that the Enterprise was in during Balance of Terror. With 3 dimensional space and the vastness of both the Federation and the Romulan Star Empire, some location may be much closer than others.
Additionally, advising Starfleet Command may not mean contacting Earth. Likewise, Barstow and Earth Outpost 4 may not be close to Earth.
So, how many days does it take to travel from Earth to Romulus? The world may never know.