The challenge of having a girl suck your dick and make you ejaculate with 10 minutes. This proves that they really like/love you because they've really gotta put forth some effort into that 10 minutes.
Guy 1: That was the best bj ever! I love the 10 minute challenge!
Guy 2: You only lasted like 3 minutes....
Guy 1: Did you get a blowjob recently?