Not SOP. Basically, a flexplate is an inert piece of metal. There are no moving parts, figuratively speaking. As long as the ring gear is in good health with no chipped teeth and there is no visible evidence of cracks, such as sharply defined and intersecting rust tracks propagating across the face of the flexplate (typically, oriented sub-concentric with the crankshaft flange), there are no chunks of metal missing (having broken out), or other visible distortion, and you are not replacing the transmission with a different type that requires a different design, then there is no real cause to replace it unless you just want to replace it.