The amount of time the couple dates before deciding on marriage has increased with each new generation.
If you have fallen in Love with your mate, is it a sin to imagine yourself "fulfilling your marital duties" to someone whom you see as your potential spouse while you wait for the right time?
(I avoided saying "imaging sex with someone you love" because I wanted to be clear that this isn't a case where the thoughts would cause me to actually divulge into those actions. I am asking merely the principle of the act, not whether it would be wrong because of what it would lead to sort of reasoning)