For what it's worth, I have decided to monitor my oil pressure from new oil change and see how it changes as the oils thins out over time (shears). I can see how vehicles with high hours at warm, low speed idle could spend a lot of time at lower oil pressures.
After my last oil and filter change here is what I've got: At start when cold (well 3-season cold, not winter), my 'fast idle' oil pressure is 59-60 PSI. Once fully warmed up, on the road at about 1400 RPM the oil pressure is typically about 48 PSI. I'm using the analog tach reading, so +/- about 50 to 100 RPM
At end of my trips, all warmed up, in my garage, in Park, at low idle (ca. 500 RPM), the oil pressure is about 29 PSI. I'll keep tracking this, looking for a drop in the hot-low RPM pressure as I approach my intended 5K miles oil change point. But if it goes much below the current 29 PSI while warm and at low idle, I will be changing oil more often and considering 5W30 oils as others have suggested.