There isn't a perfect age, but from my experience working with hundreds of couples over the years, there is certainly a difference in couples who are younger than 27 or so. For women especially, most women over the age of 30 would tell you that your mid to late twenties are major growth years. I've noticed that many couples younger than this tend to focus their attention on a big show for all of their guests, rather than the joy of being together and making a commitment.