A survey has looked at how many dates couples typically go on before sleeping together for the first time. The figure that stood out was five. About 35 percent of respondents said the best relationship they ever had began with sex on the fifth date. To them, that moment marked the spot where attraction and comfort finally line up. The result feeds an old argument over whether patience early in a relationship builds stronger bonds. Respondents recalled the pacing of their happiest relationships with striking accuracy. Anyone anxious about how fast or slow to move in a new romance may take some reassurance from the number.