From April in Food and buffet section, my response to same question: Note you have to go to players club counter
"Just used it for b'fast on Sunday. The lady at the Cosmo players counter had to go check with her supervisor because the coupon was expired. I advised that LVA had assured us it was valid until the end of the year. Anyway she came back and said they were willing to honor it but it was a once in a lifetime deal! OK. I just smiled and got the paperwork, said thank you and headed to buffet. Buffet was very good. Fruit was best we had in Vegas."