As has been reflected here, a lot of this has to do with your individual set-up. We tow a 35' trailer with a 2500 Suburban. With this set-up, at 53' bumper to bumper, I can't pull in and out of any random gas station (frankly, most Pilots don't work either). At 7-8mpg and a 37 gallon tank, however, we can't rely on much more than 225 miles per tank, and I have no interest in starting to look for gas every 100 miles at the half-tank mark (that would be WAY too much stopping). So, any time I'm doing more than 250-300 miles, I pre-plan the gas stop for right around 175-200 miles using satellite imagery to make sure I can get in. I also always make sure I have a back-up stop in case the station isn't there any more, is backed up, etc... This often allows gas stops and bathroom stops all to coincide every 3 hours or so, and makes for a very smooth trip.
This takes more pre-planning, but that process doesn't bother me, and having everything laid out makes for a much smoother, faster, and less stressful travel time for me. We can easily cover 600+ miles in a day (longest single day last summer was 720 miles) - I'd never be able to handle those distances without being able to slide right in and out of gas stops with no problems.
