Natural Family Planning: A Thought

I have a few thoughts on natural family planning (NFP) and a few questions. Remember that I don't have any particular objection to artificial contraception. But I tend to think that there is a conceit in NFP. If someone thought that conception was a key purpose of the marital embrace then it seems to me that they would limit their intimate relations to the days that they were most likely to conceive. 

Let's make a hypothetical: If the conditions of ovulation, insemination and conception could be known with utter certainty based on feasible and simple physical measurements would restraint from sexual relations during that period of time be a virtue? What if the timing could be specified down to one day per month? How much self control would that take?

How open to conception is sexual intercourse in such conditions of near certainty even assuming it isn't just one day?

It is my belief that men and women who want to master their bodies will choose methods of restraint that actually test their self-control and restraint, not defeat any need for it by the application of science.

Of course, if men and women want to practice NFP I have no objection. They may not want the effects of hormones, or the discomfort and messiness of barriers or the risk of implants. As a method of birth control I find it unobjectionable. As a practice of continence I am skeptical and increasingly so as science gives us better understanding.