We have been exclusivly using withdrawl sinc dd2 was born. I didn't get a period until she was 12 months because I was bfing. So that is 2 1/2 years. I really think it depends on the mans ability to know when, & react. We have never once had an oops (knock on wood). I have heard of women say he usually makes it in time, I think those are the women getting preg using this method.