Does trans fluid wear out

Fluid getting old and too hot can do that. However you can also call/talk with a trusted tranny guy about that. I had a similar situation with a 200R4, when the fluid was cold it worked great but once it heated up the tranny would shift too early. Turned out that a simple switch on the inside (cost $50 to replace) was the problem. I spent an extra $50 to have my tranny guy flush the entire setup and replace the filter while he was at it.