Honestly if I was planning to get 200k+ out of one of these transmissions I would change the fluid every 50k and put a shift kit in it. Of course if you drive it like grandpa the shift kit won't help much and fluid / filter changes are all that is really needed if you drive like a normal person

The shift kit doesn't make it jerky or feel race only and should have felt like that from the factory being a performance sedan. The first time I let my 04' with 125k miles shift at redline it made me cringe because I have never felt any transmission take that much time to shift. The shift kit will take out the glide and the clutches will last wayyyyy longer. It starts to get abrasive and eats seals, clogs the valve body internal mini filters and all sorts of fun stuff. When they get caked up they don't catch the material anymore and that's when your fluid really gets bad.

If you change your trans fluid yourself make sure to clean the magnets in the pan really good. The only thing you are doing with a full drain and fill 91k miles is removing contaminated fluid (nothing dangerous about that) that may have condensation from heat cycling (mostly boils out at high temps anyway) and clutch material from normal wear. It's not like engine oil that gets a lot more contamination over time. The only thing you have to worry about with transmission fluid is condensation, contamination (clutch material), and heat (breaking down of the fluid which has to be really really hot).

Transmission cooler flush