A businessman entered a tavern, sat down at the bar, and ordered a double martini on the rocks. After he finished the drink, he peeked inside his shirt pocket, then he ordered another double martini. 

After he finished that one, he again peeked inside his shirt pocket and ordered another double martini. 

Finally, the bartender said, "Look, buddy, I'll bring ya' martinis all night long. But you gotta tell me why you look inside your shirt pocket before you order a refill." 

The customer replied, "I'm peeking at a photo of my wife. When she starts to look good, then I know it's time to go home."