  Searches for helium in the exospheres of exoplanets via the metastable
near-infrared triplet have yielded 17 detections and 40 non-detections. We
performed a comprehensive re-analysis of published studies to investigate the
influence of stellar XUV flux and orbital parameters on the detectability of
helium in exoplanetary atmospheres. We identified a distinct 'orbital sweet
spot' for helium detection, 0.03 to 0.08 AU from the host star, where the
majority of detections occurred. This sweet spot is influenced by the stellar
XUV flux and planet size. Notably, a lower ratio of XUV flux to mid-UV flux is
preferred for planets compared to non-detections. We also found that helium
detections occur for planets around stars with effective temperatures of
4400-6500 K, with a sharp gap at 5400 to 6000 K, where no detections occur.
Additionally, our analysis of the cumulative XUV flux versus escape velocity
shows planets with helium detections are found above the 'cosmic shoreline',
suggesting the shoreline needs revision. The trends we found in our analysis
contribute to a deeper understanding of exosphere evolution.
