My original GTP, an 01, wet about 110,000 miles on the stock tranny with a tune, exhaust, CAI, pulley, U-bend delete, rocker arms and some small stuff I am forgetting. That saw a lot of track time to the tune of 13.50s' I had my tranny guy rebuild it with the best stuff he could buy and that one went to 270,000 when I gave it to a friend. He still drives it, mostly highway stuff, but that tranny is still going.
I had the Buicks done the same way.
I alwasy put an extra aux tranny cooler on them. Not sure if it helps, but it sure can't hurt.