The Nuclear Spectroscopic Telescope Array (NuSTAR) enables detailed high-energy X-ray observations from 3─79 keV, but its performance can be constrained by telemetry saturation when observing bright sources, leading to reduced effective exposure times. In this study, we investigate the use of serendipitous stray light (SL) observations to infer properties of an X-ray bright source in comparison to focused data. Our case study is performed on the neutron star low-mass X-ray binary GX 340+0, a prominent Z source, where we execute a spectral analysis comparing 25 SL and 7 focused NuSTAR observations. Our findings demonstrate that SL observations can significantly enhance long-term temporal coverage detecting variations in the thermal components of the system across the baseline of the mission, which could not be inferred from focused observations alone.