A survey of sex therapists published in the Journal of Sexual Medicine found that the optimal length for sexual intercourse is three to 13 minutes, with a median time of 7.3 minutes. Researchers have also found that 75 percent of all men regularly orgasm within two minutes! Read the whole post on the Mens Journal website:
http://www.mensjournal.com/ask-dr-bob-how-long-can-you-stay-erect