How accurate is the FedEx tracking?

I have a package coming and i have been using the tracker. It's been 3 days (since its been physically shipped) and The tracker is not updating. It says that the package will be here Tomorrow. I live in Suffolk county on Long Island. The package is coming from Rochester, Ny. It's 6 hours away. Is there something wrong with the tracker or is it that my package only needs to such a little distance that Tomorrow it will leave Upstate and come down to LI. Help?