I've successfully gotten them to short-check a bag on an overnight connection at IAH. (United)

The long segment was still ahead of me, so it was reasonably obvious that it wasn't a hidden-city trick or something like that.

I had an overnight stay at DXB this past weekend. It was unclear whether EK would short-check, so I decided not to risk it and went with carry-on only. I saw a post on their board this week where someone asked for a short-check on an 18-hour layover and was denied.