Oh, I see what you mean.

Well, that is problematic because there is no way to "query the world" for notes, i.e. there is no "global firehose", so we can't do something like "for all notes that exist check if they will expire". Of course we could cheat and just "get all notes from the top 5 big relays" but that is a bad idea, expensive and against my principles, so I can't do that.

I'm more interested in crazy ideas that might incentivize people to willingly go to a specific relay, like using Jumble, and post a note exclusive to that relay, like, I don't know, "if you reply to notes published on this relay 5 times and your comment gets a like from the author you get the chance to post a note to this relay that is certain to receive some attention".