There are several very unique and compelling reasons to increase your on-board fuel supply...
1. Remember when Diesel fuel skyrocketed up to and past $5.00 a gallon? I saw that coming and loaded up on fuel in advance and was able to last it out until the price dropped. That in itself saved me money, but most of all it just was satisfying to be able to do so.
2. I have passed through States with horrible fuel quality. Other States had outrageous fuel prices and/or added taxes. Having the luxury of being able to bypass them all and stop for fuel when I chose to, is priceless. Sometimes saving up to $60 or more just on one fill up.
3. Sometimes when driving you just don't want to stop, or you are nearing a big city where you would rather just get through the heavy traffic and out the other side. It's nice to have the option to just push on if you wish to do so. To be able to drive when you want, and stop when you want is a very appreciative benefit to enjoy.
4. However, on long trips there is also a real "science" to all this! Being able to out drive your bladder does not mean the downtime is identical if getting fuel at the same time. While trailering for instance, I can drive at least 800 miles on a tank while stopping just once for a rest stop as opposed to two fuel stops in between saves a lot of time, and money. You can pull off the Interstate into a rest area to relieve yourself and get back on the road in under 5 minutes with very little fuel wasted to accelerate back up to speed. However having to stop twice for fuel in between would mean navigating well off the interstate, finding a gas station, finding a pump, filling up with fuel, waiting in line, paying your bill, stopping in the rest room and then making your way back onto the interstate. This all eats up a significant amount of time, and between the two stops that's at least an hour lost, or the equivalent of having to drive an average of 10-15 mph faster for the entire duration of that same 800 mile trip, thereby eating up and wasting even more fuel.
Keep in mind that idling around the pumps and getting back on the Interstate and accelerating back up to speed costs fuel too. In fact I measured the difference of having a double sized tank and averaging fuel mileage on a 1000 mile trip and I could see an easy 10-20% better overall mileage just as a result of not having to stop for fuel half as much, not to mention getting to my destination and hour and a half faster without having to drive faster.
Having an increased onboard fuel supply has many more advantages to it than most might have even considered. But once you have one, you will never want to do without.
Both time and money can be saved on long trips, as well as providing convenience and confidence of being able to find a station in the most remote areas.