First trans that Macy did for me I put about 700 runs on it with conventional fluid, and the only reason it came out of the car was breaking the rear end.
One set of clutches showed a little wear (high gear? can't remember), but overall the thing looked quite good. I understand changing fluid frequently in a ProTrans or other aluminum type trans, but on a standard 904....? Always ran a cooler, and it was tough to get it about 145 degrees unless hot-lapping. Had to be double-entered and running 8min between rounds to get it 180+.
This year, with the new Abruzzi trans and looser converter, plus the full carbon fiber trans shield on it, it's generating and maintaining a lot more heat. Not so sure I want to be double-entering the thing anymore, even with the cooler. Have to check to see what the time frame was, but single-entered wasn't too bad... about 190deg after the final round at Farmington the other week. Seemed to air-cool down to about 160 between rounds.