If the Moon was in a very elliptical orbit or if the plane of the Apollo orbit around Earth was not in the same plane as the orbit of the Moon, then I could see where the periodic windows might be grouped with long intervals, but the orbit seems rather circular (0.055 eccentricity) and NASA would be likely to keep the inclination of the spacecraft orbit in alignment with the Moon's.
Don't look at the Apollo 8 experience reports. This is a head's up.