I think you are supposed to inspect the ATF at some interval (30,000 miles ?) to see if the fluid is contaminated and/or if it looks brownish,discolored or has a burnt smell. If any of those conditions are present then, change it. I personally do a plug drain/refill every 30,000 miles. I get the recommended fluid (T-IV) at Toyota. A plug drain removes about 3.75 quarts so I buy 4 quarts. Cost last time was ~ $5.XX per quart. At 30,000 miles the fluid looked new but, I do it myself so I changed it anyway as insurance. Ed
