GA4: first_visit event

Last update: 14/12/22

: The first_visit event is collected the first time someone visits your website." 

Question: For how long the data are stored for that user not to count again first_visit?

Answer: The user will be recognized as long as GA cookies in that browser are stored.
Browser is cleared? - first_visit will be sent again.
Different device is used? - first_visit will be sent again.
Default storage time is two years, but right now that limit differs based on browsers.
On iOS it might be days or weeks (depending on how often user comes back to the specific site), on other browsers longer.