I tried to do this on a Delta flight, leaving LAX at 11:45. Asked if my girlfriend and I could try to get on it, otherwise we'd go on the 1:35am flight (we had scheduled tickets for 1pm the following day). I am a Delta Platinum Medallion (top tier).
Agent said can't do it, 1:35am was best she could do. Finished with my ticket/boarding pass, then went to do my girlfriend's (she's also PM). Agent brought tickets over to her manager, talked for about 45 seconds, then she said as a top tier traveller, she'd let us on. She ripped up the existing boarding pass and luggage tags, and both agents rushed to get us on an even earlier 11:20pm flight.

Jeff