Interesting idea, about checking the TAN of the used Honda HCF -2 CVT fluid. While I am not well versed in anything regarding how to judge that fluid, one of my concerns was the obvious amount of fine particulates in mine when I did drains and fills on my 2016 Honda CR-V, at 25,000 and at 26,000 and at 27,000 miles +/- up to a few hundred miles depending on when I could get around doing it. I kept about 8 oz from each drain and could send some of them out for a TAN analysis if that is really a valid way to get a handle on the state of the fluid.
There certainly is a big difference in the amount of fine particulates in the fluid that can be seen by shining a good flashlight into the bottom of the glass jars I have each sample in.
Maybe someone with additional knowledge can verify the importance of the TAN in regard to the state of this type of fluid for this application? If so I would be interested to know more about this, both in regard to the samples of used fluid I have, and to how it can be used to determine how often to do a drain and fill.