FWIW in my race transmissions I use the Advance or Autozone filter kits.

Kev...that is the only way I've seen them bad as well. The original gaskets are expected to be lifetime unless some monkey reefs on them.

That'* why I got a replacement gasket for mine. I've seen so many idiotic things done to cars. My tranny pan was leaking when I got the car, and given the pain to drop the pan again I decided to just change the gasket and not take a chance.

Let'* see, I had
grease pumped all over my disk brakes,
ball joint mounting bolts left untorqued AND no cotter pin installed,
a unidirectional tread tire mounted backwards (three left mounted tires, 1 right mounted)
improperly miss-diagnosed emissions repair

Last two are understandable, people make mistakes. And no, I don't go for the cheapest repair shops around. First two are life-threatening mistakes. Sorry, I guess I'm deviating from the thread theme a little. Bottom line is nothing surprises me anymore. I'd have chosen to replace the gasket right away too.

The reusable gaskets do not leak.