Wow ! Interesting info, Aurion doesn't have an AT dipstick to check level ? Struth ! Not sure it can be done accurately with the Aurion but on my old MCV20R Camry I flush the fluid via the oil cooler lines & top up through the dipstick same amount that comes out at 2L intervals until the fluid that exits the cooler lines is clean/new.
Recently I quizzed Penrite techs about Auto transmissions & their fluids as I know little about them (I have driven only MT cars all my life = almost 30 years) & they're of the opinion it's mostly heat that destroys/breaks down AT fluid & ultimately the transmission itself. Their recommendation was "changing the fluid and filter every 2 to 3 years 38500 km to 58000 km or once a year/every 32000 km if a vehicle is used for towing or other severe service use"
They also said:
"Heat is the main concern for ATF. Automatic transmissions create a lot of friction, and friction produces heat. The fluid is constantly churning inside the torque converter and being pumped through metering orifices and hydraulic circuits. Every time the transmission shifts gears, the clutch packs generate even more heat that must be carried away by the fluid. The greater the load on the transmission, the more heat it generates and the hotter the fluid gets. Most ATF can withstand normal operating temperatures of around 90C for tens of thousands of kilometres. But if the temperature of the fluid rises above about 104C (220 degrees F) the fluid starts to break down quickly. Above 150C, fluid life is measured in hundreds, not thousands of kilometres. Above 200C, the fluid can self-destruct in 20 to 30 minutes! ATF contains ingredients to improve its oxidation stability as well as other additives to reduce foaming and inhibit corrosion. Over time, the protective additives can also break down causing the fluid's lubrication properties and viscosity to change for the worse. That's why fluid breakdown is the leading cause of transmission operating problems and failure."
Full synthetic oils last a lot longer but consider it as a safety net.