Here's what I read when researching auto transmission issues.
For automatic transmissions if the fluid is changed at normal intervals from the time the car is new, then continuing to do so has no ill effects.
However if the fluid has never been changed at regular intervals you risk breaking loose deposits inside the transmission fluid channels and valves which can damage your transmission to the point of needing a rebuild.
If the flush isn't to expensive give it a try.
If it is expensive, consider that now's a good time to swap to a 5-speed.