Who knows why the Maxxis ST tire failed but I doubt it was from poor manufacturing processes as so many of their competition is known for. Glad to hear that thus far the newly designed Carlisle ST tires are performing well, nice to know that there are some quality options besides just Maxxis when it comes to ST tires.
I set my tire psi at the beginning of any RV trip and don't mess with them much afterward unless I see a reason to. Not worried about variations in psi as the tire engineers have factored in these occurrences when they spec a tire.