This has come up for me very recently with the multi-week AO3 outage. I'm not a huge user of that site, but it specifically existed as a comprehensive archive of fanworks and of many prior fanfiction sites that have gone offline. I really respected the Organization for Transformative Works as a non-profit with a very targeted mission of archiving these sorts of works and keeping them safe from linkrot and the algorithmic web. Now, after a security incident (which I am assuming is related to the recent LLM-driven discoveries of unpatched vulns in open source hosting software), the whole archive is offline for the next few weeks.

I'd always assumed that OTW would keep AO3 online until the end of time. It, somewhat like this site, was one remaining gasp of Web 2.0 before the algorithmic feeds took over.