Do you mean change transmission fluid and strainer?
I recently changed my transmission fluid and strainer by myself @ 56,000 km and not one problem. All transmissions I have done have been fine. I heard people say the transmission failed after changing their fluid transmission. I believe it may have to do with the color and condition of the fluid. If it's bad don't change it at once time. Just change your transmission fluid with strainer every 60,000 km you won't have a problem.