Is there a low velocity level that is considered reasonably effective?

I know that very low velocity levels are best and tend towards blue on Stationview. But, most of us cannot achieve that consistently. At this point, I seem to be “hearing” quite well, with Earthquake detections at the 5.0 range out to 8200KM and a resting velocity average of about .4. Would it be diminishing returns to try to lower that resting average? What would I be likely to gain, in the experience of those who have done so?