The new monthly updates usually roll in after two to three weeks time. Since Gnome is so tightly integrated with the rest of the system, big updates for Gnome usually only happen when a new release of Fedora is shipped. KDE frequently will distribute even major releases midway through the cycle since it has fewer dependencies in the rest of the system.
This wasn't always the case. In early Fedora releases, you had to go offsite if you wanted the latest KDE for Fedora. But now that Rex has come on board (who was doing a lot of the packaging of the offsite KDE), we get the new packages much more quickly. Yay for Rex and the rest of the KDE packaging team. There are still a few bits that Fedora doesn't want to package that you need to pick up elsewhere if you want them, but it's still much better now than it was before.