Faith and Goodman Brown have not been married long. The text says three months.
What, my sweet, pretty wife, dost thou doubt me already, and we but three months married?"
Even without that direct textual evidence, the reader could probably figure out that Faith and Goodman Brown have not been married for very long. First, the title of the story specifically tells readers that Goodman Brown is young. The text also says that Faith is "his young wife." I assume that somebody who is young and married could not have been married for more than a few years.
The opening paragraphs and dialogue between Goodman Brown and Faith give even further evidence that they are quite recent newlyweds.
"Dearest heart," whispered she, softly and rather sadly, when her lips were close to his ear, "prithee put off your journey until sunrise and sleep in your own bed to-night.
That's a "come hither" line and the body language speaks volumes about her desire to be physically near her husband. It's not that older married couples can't or don't feel this way about each other; it's just that part screams newlywed to me. There are usually jokes surrounding newlyweds, because they can't keep their hands off of each other. The above line hints at that kind of relationship.