That's because it's not made for "massive horsepower". It's a street sure grip carrier that's for lighter duty applications than the clutch type Dana Power Lock. They work extremely well in their element, like anything else.
The trick to making them last is stock or mildly modified horsepower...
Remember, where the cones and case wear is on the sides of the cones where the "theads" are and the insides of the case where those threads engage. As those two surfaces wear, the cones fall further into the case sides until they hit the insides of the case. When that happens, the unit is...
I'm rustyratrod from FABO. Take some modeling clay and put a piece about the size of a marble into the case half end where the cone fits into the case. Put a little grease on the face of the cone to keep the clay from sticking to it. Now install the cone into the case and press it in as far as...