How are you guys killing EJ 5-Speeds?! My 2002 WRX was bought new by my father, we dual drove it in Autox for 5 years, maybe 10 events per year. I beat the piss out of my transmission: doughnuts and drifting in the snow, racing with multiple drivers, speed shifting, etc. The only thing we have never done with this transmission is a high-rpm clutch drop.
The engine spun a rod bearing at 80k, but it wasn't until about 150k+ miles that the center differential started making noise, which seems to be a common failure mode for the Phase 2 5-speeds.
I can't speak for anyone's experience but my own, and my experience it that if treated with even a modicum of mechanical empathy, the 5-speed transmission is as strong as it needs to be for the WRX. Heck, my 2002's "AA" transmission is the weakest one the USDM WRX was ever delivered with, still no problem shearing gears.