@logic forever or until the user/admin deletes the account, but then it potentially exists on other servers still. basically once you post something on the internet its pretty impossible to ever completely remove it.

@@logic @@liaizon Some projects expire old content that is on their server and came from elsewhere after a month or two (this is generally a good thing because it's creepy for all your friends to keep a copy of everything you write forever and it also keeps servers running happily and efficiently). Some projects provide an option to automatically delete your own content after a period of time. So it depends on what software you use, where you do the search, and if the site you're searching from honours content deletion. Reputable sites do, but we're talking about the fediverse and "reputable" covers a wide swath of behaviour that you might not personally agree with.