source from
http://nydailynews.healthology.com/n...news/16354.htm
How long does sperm live after ejaculation?
Although sperm can live for many weeks while in the testicle, sperm remains capable of fertilization only 24 to 48 hours after ejaculation. The woman's egg can probably only be fertilized for 12 to 48 hours after ovulation.
People often use this information to determine when it is least possible to get pregnant with unprotected sex. These methods are called the rhythm methods of contraception. Rhythm methods are not reliable methods of contraception. Pregnancy rates in some field studies using these types of methods were as high as 20 percent. Furthermore, they do not prevent the transmission of STDs such as HIV.
Can a guy hold his "come" inside during sex, or is an orgasm uncontrollable?
Male sexuality is extremely variable. Most men ejaculate within two minutes of penetration during sexual intercourse, then lose their erection and experience a refractory period. Some men can prevent ejaculation and experience multiple orgasms without ejaculation and without losing their erection. Although most men who experience multiple orgasms develop that ability naturally, some men are able to develop it with training. This is accomplished by a combination of interrupting sexual intercourse before a point when ejaculation is inevitable, deep breathing to reduce the building excitement, and contraction of pelvic muscle to inhibit the secretion of semen. A helpful guide on this matter is one called "The Multi-Orgasmic Man," and a guide for a wide range of questions on human sexuality is "The Kinsey Institute New Report on Sex."