I think Hy replace at 80k, this car was a bit over as the daughter is always driving it. She has University commitments and hospital placement, so it was a bit late getting done, IIRC 82k kms. I opted for a trans specialist to ensure that the torque converter was emptied and flushed as well. It was a bit more expensive as they charge like wounded bulls for the oil but assuming thay actually performed the job properly, I know all the oil is nice and fresh.
If a drain & replace is performed, you still have a quantity of old oil in the system which contains friction material and has been repeatedly sheared severely and I don't think that is a good idea at any time. Same as changing part of your engine oil, it's just not done. I always change both engine oil and filter for the same reason. The FD Hy autos have occasionally had issues with the valve mechanism. I haven't yet and I don't want to in the future.
The other car (Ruby) will get the same treatment, she's @ 55k at present.