It should say,Ooma.com says:
What is the projected battery life for Ooma Home Security sensors?
The projected battery life of all sensors is approximately 1.5 years. Battery life is impacted by usage, so sensors that are used less frequently may a longer battery life than sensors that are placed in heavily-traveled areas.
"Battery life is impacted by usage, so sensors that are used less frequently may have a longer battery life than sensors that are placed in heavily-traveled areas."