In fact, Apple's official policy is: within one year, batteries with less than 80% health can be replaced for free. In daily use, try to ensure the standard of electricity consumption, that is, try not to play while charging, and do not over-discharge the battery, that is, often use automatic shutdown, or only a few percentage points of electricity is left.
Then the battery itself is consumables, and we pay attention to the daily use experience. In other words, whether there is obvious feeling of battery life decline, if there is obvious feeling of decline, then you can replace the battery, if not, continue to use it.