I make it a habit of changing fluids early--early in the life of the vehicle--especially on my 4wds. Every vehicle I buy, I swear at the time I will "...keep it forever..." It rarely works out that way, but that's my mindset going in (also why I have a small cadre of friends who "lurk" around all my prior-owned vehicle sales to buy sight unseen b/c "they know how I take care of my vehicles") My whole life and career have been built around caution and mitigation of threats and yet, I'm still still fun at parties ;-). So it, makes sense that it carries over to any complex machine or people I care about.
Some vehicles I have done at 3K, 6K, others at 10K, and I will probably do this one at 25K. Believe or not, one of the worst offenders was the 3K rear diff fluid change of my 2011 Chevy Tahoe.
I have had fluid come out like it was brand new, and I have had stuff come out jet black. That suggested service schedule is a decision made under the scrutiny of lifetime service amortization. "Maintenance free" is a good selling point.
IMHO, vehicles and some parts take at least 8-10K to fully seat and break in. That is when it is hardest on the fluids and full of the most pollutants and debris. The rear end tend to always be the worst, I have found.
It is a personal decision, and not everyone is going to be right all the time, at every point, at every vehicle. But look at the rear end issues popping up here now. Could an early fluid change prevent it--reduce it? Make it worse even? Or using it once a month to remind the diff it has a clutch locker be the right answer? Both?
With all the factory installed complexity and shy dealers, consider getting a coupon and let them do it. Watch them if you can, and take pics of what comes out. I'd not want to takes this to a Jiffy/Mule & Fuel and have something go wrong with these spaceships. My recent experiences with Ford have not given me a good feeling about warranty claims. With some things, you want them on the hook.
Rant Switch--deactivated!