To my knowledge, the Pope, or at least the Church in general has NOT claimed that NFP is only to be used in extraordinary circumstances. It is to be used until you want anoter child.
I fully understand the hardships involved in following the precepts of the Church, and I personally am not casting judgement. Here is truly a case for ones own conscience.
I'm just stating what I believe the orthodox rules are.
The Church recently bestowed Sainthood to a woman who gave up her own life so that her unborn baby might live.
This is not true. The need for "grave circumstances" has been reiterated many times. Here is Pope Pius XII in Allocution to Italian Midwives:
The individual and society, the people and the State, the Church itself, depend for their existence, in the order established by God, on fruitful marriages. Therefore, to embrace the matrimonial state, to use continually the faculty proper to such a state and lawful only therein, and, at the same time, to avoid its primary duty without a grave reason, would be a sin against the very nature of married life.
Bad language that feeds the anti-NFP crowd.
NFP *may* be used, provided you aren't shirking your responsibilities to society.
Your other wants at age 25, for example, have significantly more weight than your wants at age 39, if by that point you have been married for a long time and only had one child.
There is certainly no requirement to use it ever, which is directly implied by using the word "is".