The short answer; depends on what sensor, network, mounting place, and network conditions you have.
Under “normal use,” following our recommendations, the battery life is expected to 10 years. See this test and verification report.
Like Z-Wave Strips, they are optimized for low power consumption that, under the right circumstances, last 10 years, or more. However, this is highly dependant on the profile settings. Please verify your expected battery life with our battery calculator.