I'm afraid the current Nostr relays don't handle the pushing of events with random timestamps correctly. For example, Alice and Bob are chatting using NIP-17, and both of their chat apps are active. Alice sends Bob a message with a random timestamp from 48 hours ago. The relay not only pushes this message to Bob but also re-pushes all the messages that Alice sent to Bob within the past 48 hours. Alice then sends Bob another message with a random timestamp from 24 hours ago. The relay not only pushes this message to Bob but also re-pushes all the messages that Alice sent to Bob within the past 24 hours.