I've taken my '20 XLT FX4 MAX on two fall hunting trips comprised of multiple ~1000 mile legs from NC to Northern MI, to WI, to SD and back to NC over 7 weeks. When I leave home, the vehicle is jammed with dog, dog stuff, hunting gear, ammo (can't rely on buying any anywhere anymore) tools for working on the cabin, hunting clothes for everything from 75 degrees to 0 degrees, light construction to formal dinners. 2 cases of wine, food that can't be bought in the great white north (caviar, limes, dry aged beef, etc.). The MAX is full to the ceiling. My previous long haul vehicle was a 2007 F150 Lariat that is now the around town vehicle with 200K on it.
Biggest surprise is the mileage. I drive 10 mph+ over all freeway speed limits, even in SD (judge away). Lots of off-road 2 tracks, mud, etc. trying to get to places others can't. I average over 19 mpg on 87 octane, while in the economy (leaf) mode. With my truck on the same trek, the best I ever did was 17 and 15 was typical. I've also taken a couple of 5 hour hauls to the beach with bikes on a receiver mounted rack and experienced NO degradation in economy. Trips that cost me 2 mpg with the pick-up.
Tips for long haulers:
Have your brand new Expedition aligned after a 1000 miles or so. The front ends shake down and settle out after a few miles. The Ford specs allow negative toe...Make sure you have a trusted source (or DIY) and stipulate that the front toe be set within the positive side of the spec. Otherwise you'll experience wandering which can get onerous on hour 1, let alone hour 15.
Take your spare tire off, get it balanced (Ford doesn't factory balance the spares) and put it back on with the face facing down. This allows checking/filling it without dropping it in the future. You don't want to do 100 miles on an unbalanced spare, let alone 500.
Read the many comments about the Hellwig stabilizer bars. Many here swear by them. I like the rear so far. I put it on at Christmas. I'm going on a couple of medium (5 hour) trips in the next few weeks...I'll decide whether I want to replace the front or not based on how it feels with the rear only replaced both on and off road.
Disconnect the small antenna lead to the liftgate "kick" sensor located inside the rear bumper cover on the driver's side. The kick sensor on the lift gate NEVER works when you want it to; but, dogs, kids and you will activate it accidentally when you don't want to over and over.
If you're good with computers and vehicles get the cord and the Forscan software. If nothing else, program out the "double horn beep" that ticks you, your wife and your neighbors off every time you step out of the running vehicle with keys in your pocket. Imagine how good it feels...once you stop beating your head against the wall....that's how it feels once the double beep stops. There are lots of other mods you can make with Forscan depending on your wants/needs.
If you plan to use the 110V outlet on long trips, check out my entry on how to tighten it up. Otherwise, you'll have to continuously reach back and re-plug whatever you have plugged in.