I've had many blowouts, and I take all the precautions. Run below 65mph, check pressure before moving the TT, and check the tires carefully before each trip. Trailer tires are going to fail. On all my blowouts, it certainly looked like they failed in the sidewall first. Some were too shredded to definitely tell, but that's what it looked like.
Blowouts are inconvenient and delay your trip. The worst is that they can be dangerous. You could send tire pieces into other traffic, you could lose control, or you could do serious damage to your TT. It's worth the peace of mind to replace them.