I'm assuming you mean lunar L4-L5. Those are stable Lagrange points, but have a fairly weak potential well and it would be trickey to manuver into them, with plenty of manuvers to keep them there.

I think a better idea might be a pair of satellites in a highly eccentric (lunar) polar orbit, apoapsis above the landing pole.
This would keep them lingering above the horizon for the majority of the orbit. Phase them so at least one is over the polar horizon at all times. Even one would be sufficient if continuity isn't required. There was a Soviet satellite that did this over Eastern Europe, what was it's name....?

I guess another benefit of this would be fairly close coverage of the opposite pole, the satellites' periapsis. Fly some packages that LP didn't have and do med-high res science of the pole not visited by a lander.