Apple's battery life does not need to be replaced too much before it reaches 84%. Battery health refers to the percentage of battery capacity relative to brand-new batteries. Once the battery health drops below 80%, it is recommended to consider replacing the battery in time to ensure the normal operation and endurance of the equipment. The decline rate of battery health will be affected by many factors, including frequency of use, charging times, ambient temperature and so on. It takes about three months to reduce from 84% to 80%. This is only a rough estimate, and the actual situation varies from person to person.