Instead of having a hard reset of the entire thread at X time, I would keep a single live thread always on, and make the old messages disappear one by one when they're older than 24 hours.

That way you would have a more continuous flow of messages from people all around the world.

You might want to keep a log of these old messages though for future searches, those can be created after 24 hours have passed, like a snapshot of what was there at the live one.