Data retention is kind of meaningless in this context since there's so many ways it is laundered/absorbed/analyzed while not technically violating whatever legalese they use this month.

Does that only apply to API usage and not ChatGPT the web app?

It would seem to, because the web app doesn't seem to expire your old chats.

My old chats all completely disappeared in the past few days . Quite disappointing actually. I had some valuable state in some of them.

Yeah, only the API. To opt out of the app, you’ll need to fill out a Google doc https://help.openai.com/en/articles/7039943-data-usage-for-c...