Transmission fluid

it's up to you. toyota calls it lifetime, while some here think it should be changed if you're planning to keep the car long term.
there have been very few tranny failures over the last 20+ years. it is the most reliable part of the car.
if you wish to change it, you'll have to find your own comfort level.
some do it every 50k. others at 5k and every 30k. others at 100k. others test it and then decide based on results.
it's all over the board, and you have to decide for yourself.

 

Required time and/or mileage? Short and simple answer is: It is not required at all for the life of the vehicle (assuming no one ever opens up the transmission or the vehicle is never flooded, or someone doesn’t decide to add fluid to and doesn’t add the correct fluid or amount).
Can you or is it a good idea? It won’t hurt anything if it is done correctly.
However, see the simple answer.