Do URLs with 4-digit keys generated with the "copy link" function expire?

[fongaboo]

I have a 'download' folder that isn't wide-open. But my understanding was that, with the right config, you could right click a file, choose 'copy link' and get a URL to that file ?k= on the end.

I do get those, I copy them and test them in an incognito window and the work fine. But then the person I sent them to later will tell me they got a 403 error. At that point I try incognito window again and get 403 myself?

So how do I keep these 4-digit-key links working for longer? If that is what I'm perceiving is going on...

Thanks!