is it known how long a hash lasts without doing much (or nothing) with the file?
The hash itself lives forever. I suspect you’re referring to the availability of the data that that hash refers to. It will last as long as someone on the network makes it available. This could be yourself, someone else who has requested the file and made it available, or someone you are paying to make it available like a pinning service.
Thank you for the response. So suppose I upload a file and get a hash. And I leave it (if possible) on this website as long as this hash is linked to this specific file. Suppose I remove the file from this website and save it in my laptop, then the hash of this file is gone. And is it reused by someone else? I understand so well. Thanks again for any response.