Why wouldn't it be friendly? 

 Just ive noticed clients use timestamps a lot to limit their reqs.. and tend to be very timeline centric.  They won't usually see old notes.  Tho that doesn't explain why they can't pull a specific eventID from a specific outbox.  Relays also can tend to limit old messages, unless they're serving backups capability, so that would make it important that the outbox gitlost uses supports very oldness.