Let's see, 18.6 (fuel tank capacity) X 16.2 (what I get currently driving surface streets with little highway/freeway driving) = 301.32 MPG. That's acceptable, IMO. I've used nothing but, 92 octane premium in my X since day one, just for reference. I also now have a Livernois 93 tune installed so, I expect mileage will go up a little. I think I can expect to get the rated 22 MPG for highway driving and would not be surprised to get better than that. So, 22 X 18.6 = 409 miles. Again, quite acceptable and what's not to like? I would be 'taking a break' every couple hundred miles so it would be rest stop then, gas station.
When I had my '13 Mustang GT/CS with the 5 litre, I easily got 26 MPG highway while crossing a mountain range (Cascades). It only had a 16.7 gallon tank and with that mileage, I could expect to go in excess of 430 miles. The size of the tank didn't really figure into how far I could go on that tank within in reason and to my mind, that was quite reasonable. I suppose if you want to get 500 miles or better these days, you'll need to get a rig bigger than an Explorer or keep the Explorer with the 25 gallon tank. But, does it really matter that much? No matter where you go or what size tank you have, you'll still be spending just as much on gas, depending on your mileage. The only difference is, are you going to drive further than a couple of hundred miles at a stint. I know that when I drive a long distance, I never have gotten to the 'E' before filling up again mainly because it's not a good idea with the fuel pump in the tank and the need to keep it cool. When the low fuel indicator turns on, I'm looking to fill up.
I know that people are different and have different ideas on this stuff but, I don't really think it is so different than how I approach it.
As far as having a full size spare, that would be nice but, it's not happening with the new Explorers. Having that as a must is limiting your variety but, if you are prone to flats, I guess it is a big priority. I can count on one hand the times I've had a flat over the many years I've been driving and only one time I had to pull over to change it out and that was less than a 1/4 mile from my home. Recently, I got a screw in one of my tires on the Ex and it went flat in my driveway. I found out about it when I was going to drive the Ex as the tire warning light stayed on when I started it up. Upon inspection, it was the right rear tire so, I took out my portable air compressor and filled it back up and went about my business. When I returned, I thought this is a good opportunity to change out that tire and try out the puny spare that was supplied with the Ex so I changed it out. The next day, with the puny spare mounted, I went to my local Goodyear to get the real tire repaired. I drove on that puny spare up and back and all I wanted to do is to get that thing off of their and mount the real tire back on. With that spare mounted obviously, the tire warning light remains on and I found that a bit annoying but, the bottom line was, it forced me to get the tire repaired and back on the Ex using that puny spare. That was the first time I ever used this kind of spare so my track record is pretty good in that respect. My 10 year old Ranger has one of these also but, I've never had a flat tire in the Ranger so, the spare is in the same place it was originally mounted when new, where it belongs. Other than my own experience with flats, I don't know what point I'm trying to make here so, I'll stop yapping about it.