It has been posted here that lust makes sex sinful in God's eyes and that abstaining from sex in marriage is beneficial spiritually.
As far as NFP and women's enjoyment of sex, I was referring to the fact that women are more "receptive" during their fertile times, exactly when one abstains in NFP. If other methods of sexual pleasure during that time are acceptable, then that negates that issue.
Lust is somewhat a term of art in Catholicism. You may want to take it up with the poster, -- I did not post it. Certainly, a healthy sexual appetite directed at the spouse is salutary. Some may refer to that as "lust". However, technically, "lust" is a disposition where the unitive and the procreative aspect of the intercourse are ignored and only the physical pleasure starts to matter. This is indeed considered sinful. But it is not sunful because the pleasure per se is sinful, but because it is not ordered toward love of God and love of the spouse, even though the spouse is the physical partner.
women are more "receptive" during their fertile times, exactly when one abstains in NFP
NFP is not a method of contraception. In NFP one abstains either during infertile time in order to store up sexual energy for the fertile time, or one abstains during fertile time in order to avoid a pregnancy. However, a valid moral excuse is necessary in order to avoid pregnancy. One who wishes to avoid pregnancy for frivolous reasons is not practicing NFP correctly. Please read the thread form the beginning if you feel like understanding what these valid excuses are. The fact that the female body is naturally oriented toward achieving pregnancy points to the fact that in natural law, any attempt to avoid pregnancy needs a valid morally excuse.
Sexual acts done for pleasure alone (even a passionate kiss) are mortally sinful. Pope Alexander VII condemned the opinion: "It is a probable opinion which states that a kiss is only venial when performed for the sake of the carnal and sensible delight which arises from the kiss, if danger of further consent and pollution is excluded." (Denzinger 1140)
So all sexual pleasure involving arousal that does not conclude in intercourse with the man climaxing inside the woman in the normal way is mortally sinful. Hence all complete acts of oral sex on a male are mortal sins, and all complete acts of oral sex on a female apart from the male either before or after climaxing inside the woman in the normal way are also mortal sins.
So all methods of producing sexual pleasure in a woman apart from the man completing it with an act of marital intercourse must be entirely excluded as mortal sins.