I have an 02 WRX thats my own "stage 4" combo...I modded it like it sits now at 5K miles in 2001. Car now has 63K miles on it and runs like the day I got it tuned.
When I didnt know what I was doing I blew a tranny, replaced it with another stock one (including oem clutch/flywheel) and I have about 40K on it. Testament to the fact if you treat it right it will last.