Stayover relationships

Just as the Christian churches in the West seem to be getting a handle on cohabitation, along comes something else to make life difficult for working with principled relationships.
Trend in young adults' dating habits, committed relationships may not lead to marriage: "found that 'stayover relationships' are a growing trend among college-aged couples who are committed, but not interested in cohabiting. However, little is known about the effects of stayovers on future commitment decisions or marriage.
'A key motivation is to enjoy the comforts of an intimate relationship while maintaining a high degree of personal control over one's involvement and commitment,' said Larry Ganong, professor in HDFS. 'We see this interest in personal control nationally in more single adult households, and in the growing phenomenon of 'living apart together' (middle-aged and older monogamous couples who maintain their own households). It may also help explain why marriage is on the decline, particularly among young adults.'"
So how to evaluate? How to engage constructively and critically? How to disciple?
Any lessons from the last 30 or 300 years?