Are uploaded files permanently available when using the ASSISTANT API?

I created a slackbot that works with the openai assistant api.
I uploaded a text file with frequently asked questions and answers to the channel, and when users ask questions, the slackbot uses the retrieval tool of the openai assistant api to refer to the contents of the uploaded file to deliver the answer.
If the assistant session disappears after a certain time and the uploaded file is also automatically deleted, my slackbot will have no documentation to refer to.
Is there any way to solve this?
Any advice would be appreciated.

Hi and welcome to the Developer Forum!

To the best on my knowledge, files that are uploaded are persistent across sessions and assistants, so that should not be happening, can you provide some more detail please.