what causes my oil pressure to fail after my engine gets to operating temp?

Debris in your oil pump pick up screen, caused by something inside the engine deteriorating. Dropping the oil pan will give you more clues.

I have the same issue but w/ a 2001 Dodge 4.7. What I've read is quite interesting.One possible cause is a worn main bearing and a high weight oil. As the motor warms the oil, it tends to thin, reducing pressure as the path the oil travels through has been enlarged due to the worn bearing. There was a recommendation to add a thicker oil. Perhaps 10w30. I tried that but didn't see any improvement. The next step I will take is to drop the oil pan and check the oil pickup screen for sludge blockage... Good luck to you. This is a real pain in the butt!!