How to change fluid cooler line OR multiple D&F

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ok here is the deal. I have a new to me 98000 mile Subaru Outback H6 4EAT. 9.8 qt total fluid capacity I am assuming the transmission fluid had never been changed, I have no definitive proof either way.
I immediately did a pan drop cleaned magnet and re-istalled, fluid was a brownish red, plenty dark but didn't smell burnt and was extremely low on any clutch fluid, looked text book good, no excessive clutch material and zero little bits or chunks. now I have 200 miles on the 4 qts I replaced (maxlife dex). It did immediately shift quite a bit better you could tell it was ready for some new atf.
Here is my grand question ?
in the past I've always done it this way drove it a week or two, then change the external filter, pull a cooler line and with the help of another start and drain 4 qts at a time from the transmission input to radiator line, while i dump new fluid in through dipstick. I do this three times exchanging a total of 12 qts through a 9.8 qt capacity transmission.
my question is do you feel this is better this way. or would I be better to change it 6 more times over the next year... try to get 5 more 3-4 qt changes throughout the year ? If doing a multiple D&F I would try to get at least 3 more within the next 1000k and another filter change at that point then spread the last 2 over 3000 mile intervals.
D&F - Contaminated Fluid Remaining
1 --- 6.43L
2 --- 4.12L
3 --- 2.63L
4 --- 1.69L (17.6%)
5 --- 1.08L (11.3%)
6 --- 0.69L (7.2%)
7 --- 0.44L (4.6%) I have always done the pull a cooler line exchange, but it seems to foam the atf a lot and I am wondering what percentage rate is clean atf, I've always been of the school of get the new stuff in there, but am wondering if giving it a little time to let the trans adapt to the new fluid and more filter changes would be more tender to the transmission. I want to own this car long haul....
I have just seen both trains of thought on here as to doing the cooler line vs multiple d&f, not worried about an economic point of the fluid changes, I would rather have a transmission last longer fluid is cheap in the over all picture, ok now I've wrote a book lets hear what your opinion or ideal way would be... oh and after this is done ill stick to 30k intervals with a filter change
 
If your objective is to change as much of the fluid as possible, then the cooler-line method is more effective.

Also, why do so many people insist on driving long distances in between when doing drain & fills? It seems to me that simply driving the car around the block would more than sufficiently mix the new and the old. Assuming the intent is to get out as much old fluid as possible, just do 2 or 3 back-to-back D&Fs with a quick drive in between.
 
Originally Posted By: Dupree
I am wondering what percentage rate is clean atf


"When doing a transfusion style exchange, a good general rule is to exchange 20% more fluid than the total vehicle capacity, which will give a 90% plus rate of exchange rate."

http://www.cloreautomotive.com/uploaded_files/product_knowledge/12_CPK ATF Exchange.pdf

Originally Posted By: Dupree
my question is do you feel this is better this way


The only tangible difference between varying methods is efficiency -- a one-time exchange uses consideribly less product ($$$) and time to accomplish the same task.
 
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