The thing about having an aux tank is not about bladder and stops, it is about comfort. I put an aux tank (45 gals) with tool box before going on a trip to Colorado in October. Seems like my only fuel was filling my aux tank every morning before pulling out, and still having 34 gallons left on board the truck for emergency stops or not having to stop. It was a great stress reliever for fuel .
great investment that takes the stress off, and comes in handy if you are stuck on the interstate. Got it from northern tool with the gravity feed and the shutoff valve.