Aww Lisa I didn't say your doctor was wrong. I agreed that sperm can last longer than 72 hours. However, after this time they are less likely to be healthy and to fertilise an egg. That is what our data says. In a laboratory setting there are far fewer sperm left after 72 hours than in the first 72. It is amazing to see them all bizzing around and slowly they drop off. However there are certainly some there just fewer with less healthy structure.

As Ryn says when there are optimal conditions (ie ewcm) sperm can swim around longer and retain their structure.

Each practitioner will have their own view and each woman will have formed her own opinion. Even the frequency of intercourse when trying to conceive is a point of conjecture amongst many of our experts.

Some recent studies reported in a recent journal have stated that daily intercourse is the best bet if trying to conceive. Also that couples should be having intercourse frequently throughout the entire cycle for optimal sperm motility. The secondary reason given for this was that some ovum will survive 12 hours or less and therefore frequent fresh sperm is the best bet of conception.
Other 'experts' say second daily intercourse is best. So, I guess each clinic and each practitioner will have their own opinions.

Of course as all of us on this somtimes frustrating trying to conceive journey know that intercourse in the days prior to and close to the time of ovulation gives the best chance of conception.

My girlfriend conceived her daughter with a single act of intercourse 4 days prior to her expected ovulation - it most certainly does happen!

Ryn also highlighted the reasons why more boys are conceived when intercourse occurs on or around ovulation than in the days before. That certainly works for me personally - and I have seen many many women succeed with using those theories. However, you will still see stories contrary to the 'rule' as nature will often defy science in my experience at least!