‘Forever’, as long as the node exists. Yes, same for DM’s, only that those are encrypted and only the participants can read those.
Discussion
So storage requirements continue to grow. Seems like a problem for relay owners.
Yes, but its just text, so it is not that much. Also you could set up a relay for your friends and family, it would only store their and your content i.e. but also on all the other relays everyone is connected to.