For my E320, once reset I notice an immediate sense of power gain since the engine will respond more with less peddle pressure (shift points are at a lower RPM). It usually takes a few weeks before the trans adapts to my normal driving habits. I thought I read it is related to about 50 starts.

I assume that you have checked the trans fluid level at the proper temperature.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles