Rushing Into Premarital Sex

A couple that has enjoyed a blissful connection could suddenly descend into relational issues with no warning.  However much time has been invested into a relationship, platonic or romantic/sexual, you do not know if you will marry someone or stay married to them, even if only because one cannot know their mind or the future (one's own mind is absolutely certain).  This does not mean relationships must or will end in this manner, only that it is possible.  The time a relationship has been established does not exclude an abrupt change in one or both partners.

No, it is not known if someone will remain with their partner; someone could break up unexpectedly for trivial reasons or because they suddenly had a metamorphosis of worldview or personality, not that there is anything other than simply desire stopping people who are legally married from doing the exact same thing.  Legal marriage does not and cannot stop the dissolving of a romantic partnership if just one party is unwilling, but it can express commitment that would last through trials whether or not a couple has a legal union.

It is still true that people do not know how long they will be with a partner even if there are no obstacles to lifelong intimacy at the moment.  This is part of why, although premarital sex (sex before legal marriage, that is) is not always sinful since it is not inherently noncommittal, objectifying, and so on, it is still not something to rush into by any means.  If one is morally obligated to commit to one's consensual sexual partner of the opposite gender if one is unmarried or unengaged (Exodus 22:16-17), then it is still not at all a casual thing, as in that case, the "punishment" would be marrying one's partner.

In this way, premarital sex--since sex can initiate or establish a Biblical marriage as well, as there was no government around when God created the first humans and thus its presence and approval would by necessity be objectively irrelevant--is a thing to be done carefully even when there are no indications that a couple will not last.  Rationalistic people who genuinely love each other and do not mistreat each other might turn out to not be a good match as far as personality goes, and people can drift apart even if they do not wish to.  Sex outside of legal marriage needs to be done with sincerity and with some degree of direct (between the two participants), mutual commitment.

This would entail that no one is hurriedly making the decision to have sex with a romantic partner of the opposite gender.  Even if premarital sex was sinful, and it is not in itself according to the Bible, other forms of sexual activity like oral sex, sexual fondling, mutual masturbation, and sexual display of the body (full, sensual nudity is never sexual, as only the intention or way it is handled is sexual in specific cases) are entirely permissible between consenting men and women (Deuteronomy 4:2).  Premarital sex is a more intimate, serious thing, and it is this act that no dating partners should rush to despite it being entirely permissible in certain circumstances.