well we usually make it through 4 laps of practice, 4 laps of first moto and 3 laps of the second moto and then run out. Track is about 1.5 miles long. so that is about 15 or so miles. Maybe more if your throttle twister isn't hammering on it.
we ride woods/race enduro/hare scrambles and at about 25 miles you will need to fill up.depending on conditions aliitle more or less.Little guy enduros do not venture too far away from pit areas so filling up during resets is not much of a problem