When she starts to look good, I know it's time to go home

A businessman enters a tavern(酒馆), sits down at the bar, and orders a double martini(双倍马提尼酒) on the rocks. After he finishes the drink, he peeks(窥看) inside his shirt pocket, then orders the bartender(酒吧招待) to prepare another double martini. After he finishes that it, he again peeks inside his shirt pocket and orders the bartender to bring another double martini. The bartender says, "Look, buddy, I'll bring ya' martinis(相当于you) all night long - but you gotta tell me why you look inside your shirt pocket before you order a refill(再次倒满)." The customer replies, "I'm peeking at a photo of my wife. When she starts to look good, I know it's time to go home."