Having owned travel and 5th wheel trailers for the past 25 years. I learned a lesson a long time ago to replace the tires every 3-4 years whither they look like they need changing or not. I had plenty of thread on the tires but they seemed to blow out or go flat when I pushed the 4th year on the trailers. Here is Southern California, our sun and ozone breakdown trailer tires over time.
2015 Ford F-250 SD 4X4
2013 Sunset Trail 32RL 5th Wheel (no longer own)