“Is premarital sex okay if you know you are going to be married?”
I have written a fair bit here about the barnacles that encrust the institution of marriage today: how matrimony as God originally designed it required the approval of neither church nor state; how rings, dresses and ceremonies are extra-biblical window dressing; how even vows are a bit extraneous.
From a heavenly perspective, little of what we do today in preparation for binding two lives together is actually essential. Frankly, even romantic love is optional.