I installed my shift kit about 175,000 km (93,000 miles) ago, due to the max adapt shift issue. I see trans temps of 195-215*F in the summer, but I don't drive far, so I just change the fluid a few times per year. 8 years later, she is still going. I don't bag on her, so that helps.

With that being said, yours may last or it could blow up tomorrow. A shift kit sure can't hurt.