A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body.
No worries about losing the altitude, orbital track or moving.
The NRHO is apparently a specific type of Langrange point orbit.
I Think your answer is here: “... but always keep a station within the line of sight of flight controllers on Earth ...” ‘controllers’ being the operative word.