this. DL used to allow until midnight the next day for a long time, but I’m not even sure they do that anymore.

Not by the rules, but I think UAs system occasionally tripped up and had a little bit of an extra period where it sometimes still allowed a refund. I wouldn’t count on it, for sure, but at least these days, at least for those of us who won’t book BE, there is always the credit available if you somehow miss the window.