When does champagne no longer fizz?

Regretably, I've never been much of a drinker, but I'm writing a short story in which a character pours some champagne and it bubbles over the rim of the glass. Can anyone tell me if my character opened the champagne at 8 p.m. and pours the last of it at 5 a.m., will it still bubble and fizz as I've described?
Thanks.