Do you know you have a big hole in your vision in each eye where the optic nerve is? It's about half the size of your fist at arm's length, and 35 degrees to the side. Your fovea happens to be roughly the same size. It's the HD part of your retina, and it's where essentially all of your vision happens. It's the only section of the retina that sees color, for instance. The periphery sees motion and that's about it.
Saccades top out at around 700 degrees per second. At 120 frames per second that's only about 6 degrees in either direction. Compared to the FOV, that's tiny. Overfill it!