Not to rain on your NFP parade
Don't worry, I have an umbrella. :p
That being said, two weeks abstinence still doesn't sound right. I'm reading about the Marquette mucus only model (which I gather is a variation of the Creighton model). They say, from when you notice peak mucus, abstain 6 days before that (or when "high" mucus is seen) and until evening on the 3rd day after. This makes 9-10 days tops. I don't see how you get from here to 14. And if you're cross checking with other signs you might not even need that, I don't know about that though.
Also, someone put a link in another nfp thread, a study by Georgetown University that showed NFP using couples did not have les sex than ABC couples. This doesn't really seem to match up with 2 weeks or more of abstinence.