Most men are able to hold an erection for three to five minutes before ejaculating; those experiencing rapid ejaculation will typically ejaculate much quicker than this.
Rapid ejaculation can cause a host of other problems for couples. Some men become so focused on lasting longer than they lose their ability to feel pleasure during sex. Worrying can make it difficult for men to sustain their erection and/or feel sexual desire. Men who suffer from rapid ejaculation may also rush through sex, causing their partners to lack adequate arousal for pleasurable lovemaking.
Most often there is no medical cause of rapid ejaculation. Instead, feelings of inadequacy, guilt, and anxiety may contribute to the problem. Some men are also hardwired to ejaculate quickly, and must train their bodies to last longer.