I'm in the same boat with my 2001 Lincoln. And in all the research I did I didn't see anything that suggested moving down from a Mercon V medium viscosity of 7.5 cSt @100 C to a LV (Dex 6) at 5.8 cSt was a great idea. Most regular Mercon V's are semi-synthetic and will shear down over a 20,000-30,000 mile OCI to about an LV spec. But there are full synthetic Merc V's that will stay up at 6.8-7.2 during their lives. Mobil 1 ATF and the Amsoil or Redline syn ATF's are of the correct viscosities and will not shear down much. MaxLIfe ATF is a great fluid....but it's not medium viscosity. Until I see a ton of evidence that the Merc V vehicles ran 150K-200K miles on "only" Max LIfe fluid, I'm not convinced it's a correct substitute.
Despite all that I use the Super Tech Mercon V (semi-syn) and have used Amalie Mercon V as well. The only ones that I know have the Ford Merc V approval are Super Tech and Castrol Merc V. I change out my ATF every 15K-25K miles based on color/appearance.
Whatever your Mercon V fluid is, change it every 20k-30k miles and you shouldn't have a problem. If you go to a Quick Lube place be aware they might put in the older Mercon/Dex 3. They've done that to me. So now I just change my own fluid 2-1/2 to 3 yrs.