[comptiger5000]

With the shift kit in, you've upped the line pressure at any given point in the curve, so the lower line pressure (lower on the curve) when it thinks you're being lighter on the gas isn't dropping the line pressure enough to hurt it.

What can happen (and would if I loosened up the kickdown cable on my Jeep with a 46RE [A518] tranny) is that it shifts too gently and the clutches slip excessively during the shift, wearing them out prematurely. A shift kit ups the line pressure curve, allowing you to sit lower on the curve, giving lower shift points, and still have stock or higher line pressure for a given throttle opening, allowing better mpg without killing the tranny.