Getting an auxiliary fuel tank is one of the best things you can do. It becomes the scenario where you stop when you want to, not when the truck demands it. If you never travel off the interstates, it's less of an issue, but get off on the two lanes and those big ol' truck stops are fewer and farther between.
Personally I'd rather stop at a city park, rest stop, or almost anyplace rather than spend time at a truck stop. And my long day of travel is about 250-300 miles. :) I can usually travel two days before I have to refuel.
I believe the newer versions of the injector pumps are very intolerant of any water or rust, so you may be better off using an aluminum tank. I have a 35 gallon steel tank, and it is the perfect size for me, but I also have an old diesel engine that isn't as fussy as the new ones.