While individuals in "friends with benefits" relationships reported higher sexual satisfaction than married couples, those engaging in "exclusive dating," or simply, engaged (like, soon-to-be-married), topped the list. So, maybe put a ring on it, but hold off on the actual vows for a while. More bang for your buck... so to speak.
*To note, the study examines sexual satisfaction and not emotional satisfaction, which might explain why your casual relationship with the childhood best friend you've been pining after since Pre-K might generally not be classified as "satisfying." Womp womp.