For some purposes it may be desirable to maintain an erection for a long time. It is clear that periods of up to an hour are not uncommon, and that if the penis is in the vagina for this time then maintaining an erection is not difficult for some individuals.

Kinsey noted that the length of time over which the erection can be maintained under "continuous erotic arousal" drops from an average of nearly an hour in the late teens and early twenties to seven minutes in men in their late sixties. It is pointed out that under prolonged stimulation "many a teen-age male will maintain a continuous erection for several hours..."