On my Lucky Duck they will last several days, but I never run in continuously. I also have the charger pack to plug in to recharge the batteries. Once I get a coyote within 300-400 yards I turn it off. Once the coyotes locate the source from a mile away they will come within 5 yards of you on either side, that is how good their ears are. I will lip squeak once they get within a couple of hundred yards. Once the coyote locates the sound I want him looking "for" me, not "at" me.