IMO it depends on the time frame and what's being edited rather than x number of minutes between post and edit.
Most typos can be fixed at any time without disturbing the discussion, even if it's continued on for pages. I've seen cases where typos have caused confusion, and the member has cleared it up in a later post.
If something's been worded too harshly and the author wants to go back to moderate it, I think that works well as long as there aren't too many posts in between discussing the comment. It doesn't have so much to do with the time frame. If I wrote something I wanted to alter later, either because I decided it was too harsh or because I saw it was being misunderstood, I might quote my own original post and write a new version - or write a post saying something like "I've edited my post above". In other words, I'd try to make it clear that I was changing what I wrote so as not to create confusion or suspicion.
I don't think it's a matter of needing to be policed, but more common sense. I think most people edit sensibly. If a particular edit looks like an attempt to troll, it can be reported and we'll look at it.
Most typos can be fixed at any time without disturbing the discussion, even if it's continued on for pages. I've seen cases where typos have caused confusion, and the member has cleared it up in a later post.
If something's been worded too harshly and the author wants to go back to moderate it, I think that works well as long as there aren't too many posts in between discussing the comment. It doesn't have so much to do with the time frame. If I wrote something I wanted to alter later, either because I decided it was too harsh or because I saw it was being misunderstood, I might quote my own original post and write a new version - or write a post saying something like "I've edited my post above". In other words, I'd try to make it clear that I was changing what I wrote so as not to create confusion or suspicion.
I don't think it's a matter of needing to be policed, but more common sense. I think most people edit sensibly. If a particular edit looks like an attempt to troll, it can be reported and we'll look at it.