Like Dave said, your riding style will directly affect how far a tank will take you. If you ride aggressive, you should be able to get 150 miles before you need to look for fuel. If you just casually cruise along, 200 miles is pretty easy to hit. An easy way to know is to remember that you will use 75% of your fuel when you have to hit reserve. So if you ride 150 miles from full to reserve, you have another 50 miles left in the tank if you continue to drive in the same manner. Usually it's time to get off and stretch a little after that far anyway, so might as well top off the tank!