Extend iPhone battery life

How long should my new iPhone's battery last before it needs replacement, and how can I extend that?

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The working life of a battery is based on how many times it can be fully discharged then recharged to full, its battery cycle.

Before the iPhone 15, Apple expected iPhones to charge to 80% of their original capacity when they had completed 500 cycles; from the iPhone 15 on, they should cope with 1,000 cycles before reaching that.