What does the perpetual virginity of Mary add to our salvation?

I tried this question earlier and it was closed due to so many other similar questions but, having looked through I didn't find an answer. What, if any, is the **salvific benefit** of the perpetual virginity of Mary? In other words, having been born of a virgin according to prophesy and all other parts of the life, death, burial, resurrection, ascension, and coming again of Christ remaining the same, is our salvation in Christ lessened in some way if Mary has moral and lawful intercourse with her husband?