The Earth has 7 Lagrange points nearby since SEL1 and SEL2 (Sun-Earth Lagrange points 1 and 2, respectively) are only between 3 and 5 LD (lunar distances) away from the five EML (Earth-Moon Lagrange) points. Can it be useful for spacecraft to move in a sequence between SEL's and EML's in order to lower their missions' delta-v requirements? Has it been done already?
I would think that the monthly and substantial variation in their relative distances and angles should help lower delta-v for a wide range of maneuvers in this wider cislunar region. The SEL1-to-EML2 distance varies between 1,100,000 km and 1,900,000 km over a fortnight, while the EML points always have stationary locations relative to each other. But my impression is that SEL1-EML connections are rarely discussed.