What I as a non-tech kinda guy understand is that clients have to somehow realize when they stoped monitoring a relay (when the nostrich goes to sleep) to then come back to it in a few hours and ask for events starting from a certain point. So if the client does not know the ordinal number of the event it last saw, it has to explain how far into the past he wants to dig, e.g. specifying dates or smth else.

If I’m right, then events don’t have to be unilaterally numbered. Only clients will have to memorise particular event number last seen with each relay.