I religiously change my atf! Bought a 2012 model (4 speed Aisin tranny)
First bought it used, changed it at 70,000 kms. Looked a bit dirty to be honest. Changed filter and gasket, new T-IV Toyota atf.
I dropped the pan and filter, measuring what came out.
New atf in, ran it for a bit, then drained it again and refilled to wash out more.

Now at 101,000 kms, just changed the filter/gasket and ATF again. Came out really clean, no particles on the filter at all which is a good sign.

I only use T-IV Toyota in my 4 speed. Mobil 3309 I believe can be used also, which I think are the same. I don't have mobil available here.
New filter and gasket everytime.

Preventative maint for trannys is fundamental! ATF is not expensive and its fairly easy to change it on this model.

Our drivng is severe, hot climate in summer and several daily short drives with severe stop/start driving in heavy traffic.