The battery life of Bondic is not different from that of any battery-powered device such as flashlights or remote controls. You can expect to get as much as 8 hours of total use from the LED light, which is an adequate amount of time considering you only need to use it for about 4 seconds at a time. You can replace only the batteries, but it is not advisable as the automated production of these items basically makes it difficult to do so.