Does the fuel pressure regulator ever go out of calibration?

Never assume anything because you'll usually find yourself wrong. You can easily test to see if the FPR is doing it's job by ... well ... testing it. Most fuel injected vehicles (and every GM one I'm aware of) has a Schrader valve located at some place on the fuel rail before the FPR which will allow you to plug a fuel pressure tester onto and give you an accurate fuel pressure reading. There's no guessing. No muss. No fuss. And definitely no assumptions.