Factory batteries are top tier and get you around 1000 charges, typically about five years. After that the battery is around 65% health and time to change out.

Apple is no different from other manufacturers in that respect, maybe better quality cells than most. They suck at making those changeable, lately. 2011-2017 Macbook Air is about a 5 minute job. MacBook Pro from certain years you just want to throw it in a lake, or scrape glue for ages.