Under normal circumstances, the sperm cell can survive about a week in a woman's vagina but there are other factors that can affect this. At least that was what our Doctor said when we had issues. The life span of sperm cells can be shortened by a number of factors and generally its all about healthy living. Alcohol, smoking, drug abuse you name it even lack of enough rest makes the sperm cells tired too. Maybe a look at sperm count and motility enhancement may help.