I can't agree with at, though. I think NFP can be kind of nerve-wracking, at least at some time, for many couples, and I wouldn't do it at all unless there was a good reason why a pregnancy would be bad news (medical, financial, every-body-is -at-the-end-of-their-rope-and stuff-is-falling-apart reasons.
O conversely, using NFP to achieve pregnancy: unless here are actual subfertility issues I don't think you usually have to make an effort to "achieve."
I think normally, people should act normally. And normally, you just have your blessed sexual relations when you blessed-well feel like it, and come-what-may.
My two cents' worth, adjusted for inflation.
I think the default with NFP is limiting the family size. Conceiving is either a positive decision or an “accident.”
Others’ mileage may vary. In fact, I know it doesn’t. Some of my friends can’t get their husbands away from sports or computer games with dynamite!