Ok, so first off, radials are much much better than bias, no question about that. I sell trailers, and the difference in wear life is very noticeable between the two. So much so, that we don't even stock bias ply tires anymore, and haven't for nearly a decade. It's hard to put a timeline on lifespan, because UV damage makes a big difference. For instance, the same trailer parked in the same spot year after year, and if the sun beats down on the tires on one side, they will dry rot and crack much sooner than the other side that is in the shade. That said, my understanding is that the recommended replacement interval is more like 5-6 years. Basically none of my customers pay much attention to that, as most of the trailers we sell are used by businesses locally here, are run every day, and wear out tires much faster than that. With boat and RV's, things are a bit different. High dollar toys that can be damaged, should a tire blow out. With my boat trailer and RV, I'm keeping a close eye on the tires, and when I start to see any cracking, they're getting replaced. Another thing to keep in mind is how close to the weight limit they're running. With both of these items, there usually isn't a lot of "cushion", so don't press your luck, especially if you're looking to take a longer trip. As for chinese/imported vs american made, that's a muddy mess. Some of the chinese/imported tires are very comparable to the american made tires, but I do believe the GY Endurance are the best on the market. We sell the Westlake brand, which are made in Thailand (used to come out of china), and they've been very good for the money. All in all, if you want the best, get the GY Endurance. If you want the cheapest, that's fine also, but don't expect great lifespan or performance, and understand you're taking a risk, so own it if something bad happens. If you want a good middle of the road tire, there are plenty of options, but I'd probably steer clear of an Amazon purchase short of a known brand. Amazon is fast becoming little more than a portal for a lot of poor quality junk from china, just like ebay did. I've been seeing more and more accounts of chinese knockoff's being sold on Amazon, and branded as the real deal. Which is disappointing, as I love the convenience of Amazon.