Update: He made it a bit over 24 hours. I was in the bedroom getting my daughter ready for bed and I heard him quietly "set" an empty beer can in the recycle bin. When I got done getting her down for the evening, he was on the couch with a stein half full of beer. Since then he's added another can to it.
I know I said I had low expectations, but am I just flat out stupid? Should I be giving him a buffer of time to undo a behavior he's had for years?