My cousin had Carlisle's on a Weekend Warrior and I think he had a blowout on every trip. They were never very old. They warantied them, but he finally gave up and went to another brand. Don't remember what.
My brother had a Wanderer with Carlisle's that were only a year old. We left on a trip and got about 10 miles from home and one blew. After about 30 minutes of fighting blocks and jack in soft dirt, it finally dawned on me to just dig out from under the wheel.
We got it fixed and made it to our destination, but on the way home another blew. Good thing I was there with my spare, a Goodyear. We made it home without any more blowouts.
As I mentioned I have Goodyear's, load G. I have a heavy trailer with only two axles, and I haven't had any issues. The sidewalls hardly flex. It was night and day when we put one my brother's trailer.
It has been my experience with a trailer that if one tire blows, then the rest aren't far behind. If your hauling much of a load, I would go with at least the E. You can't be too careful. There is nothing worse than being stuck on the side of the road, when you're on a trip.
Sorry for the long story.