the goal of humanity should be the long term stability, progress and refinement of the species.
i believe it would be more beneficial for 2 people to engage in a life long relationship from early ages, say 6, while being intelligently chaperoned by mindful adults.
the end result being 2 people having the full experience of a relationship, while never having doubts or experiencing the fear of missing out.
serious age gaps introduce an uneven engagement between two people, causing discontentment potentially causing stress on stability - which measured societal-wide would halt progress and refinement.