I do SO hate tire discussions, but this one has stayed nice and friendly....congrats! Leaning a totally different way from the ones mentioned, our ROO HTT came with Greenball Transmasters. The OEM set was perfect....not the first little problem. We replaced at about the 3 1/2 year mark as we were taking a longer trip and didn't want problems. After lots of reading, looking, shopping and fretting we found the same Transmasters online at a very reasonable price, so ordered and had them mounted locally. Again, perfect. Then, just before the 4 year mark and another long trip, we started the whole routine again and decided that both sets had been totally trouble-free and had trouble finding them online, so DH called Greenball offices and found that they are now carried at Sam's. Again a competitive price and our thinking included that wherever we might go, there's a Sam's not far away. Took our trip without a glitch and decided to move to a TT. The young couple that bought our HTT is still using them - they're only at the 2 year mark now - and have had zero problems. Something you might want to at least investigate. BTW, they are not USA made, but not much is any more.
Re tire life....my cousin's DH tended to push for "just another few months" or "just another year" and routinely had blowouts. He'd replace the dead one, but press on with the other 3. Sooner or later another blowout and he'd replace only the dead one. Repeat. Getting by on 9 year old tires...you should have played the lottery or stopped at a casino....you were absolutely lucky. Glad lesson learned. Even more happy no one was hurt and no damage.