I have a '01 ES 300 and in checking my OM, the service interval for transmission fluid is not listed for "normal" service. The diff oil is recommended for change at 15,000 mile intervals if you are towing a trailer, camper or have a car top carrier. Only time transmission oil is listed for change is at 60,000 miles (and 120,000 miles) if you are operating your vehicle while towing a trailer, camper, or using a car top carrier. Also notice on the transmission dipstick the small label just above the o ring seal. No requirement to change transmission oil under normal operating conditions. Anyway, it is always good to check the clarity of the transmission oil and to smell it. Should be pink, clear and not smell burnt. I have heard from a good friend who has owned Hondas into the 250,000 mile range about periodic "partial" drain of transmission oil and then an equal partial fill with new transmission oil, but never fully changing the oil totally at the same time.
backyard farmer