Just wanted a few opinions, do you al think Transmission Drain and Fills are really necessary to keep your transmission healthy?
The Taurus definitely benefits from PROPER transmission service. This means approved fluid and filling to the correct level.
The 30k / 3 year change is not a drain and fill but a line off exchange. In my experience, this interval seems right.
Like chart though, I've decided to do periodic drain and fills through the dipstick (I have a Mityvac). I have a spreadsheet where I calculated that 10k miles for a 50% drain and fill works out to be the same as the 30k mile full exchange.
I have used 3 different Mercon V brands and monitored transmission temperatures and right now think the Valvoline Mercon V (not technically approved) is better than the Motorcraft Mercon V. The third fluid I used was Pennzoil Multi Vehicle which claimed to meet Mercon V. I only had 6 quarts and used it for a drain and fill and didn't like the results when it mixed with the Motorcraft.
I've recorded lower temperature with the Valvoline Mercon V and this would technically mean it would last longer. But many believe the important thing is to perform the change to remove debris. My UOA on Mercon V showed it was in good condition at 16k miles but that it held a lot of wear debris.
It is probably overkill to do a drain and fill every 10k miles or sometimes sooner, as I do. Many here have long lasting transmissions with drain and fills (not full exchanges) every 30k miles or even longer. But since I have over 50 quarts of Valvoline Mercon V that I got for $1 a quart, there is very little downside for me personally if I do 10k miles or less drain and fills.
Lastly, I happen to believe that most mechanical failures are because of sloppy mechanics using the wrong fluid or leaving fluids at the wrong level. Enthusiasts are less likely to make those mistakes and on weakly engineered parts like the Taurus transmission, that may be one reason that on this forum you find long lasting transmissions with basic maintenance. In the rest of the world, it seems your Taurus transmission has as much chance of lasting if you leave it alone or ask a mechanic to service it.