Just did the 3 x 3 again. (11 months and 14,500kms on from the previous time.) Used Valvoline Maxlife Synthetic ATF again.
What came out on the 1st drop was reddish brown but the next 2 drops were bright red. No "swarf" on the magnetic drain plug which is a good sign. The changes are super smooth again.
I will do it again in 12 months time. The cost really is not all that over the hill and is certainly cheaper than a complete transmission replacement.