Age really should not be a determining factor for marriage. We were married young. (I was 19, and my husband was 20.) We have three children, 2 of which are grown and have moved out of the home, and a beautiful grandchild. We will be celebrating our 25th anniversary in October.
As to the comment of growing apart, this only happens when a couple do not make their relationship a priority. This is important because life has a way of keeping one focused on its circumstances, and before you know it 5, 10, 15, 20, etc. years have gone by. If your relationship with each other has been a top priority, then you have grown with each other through the years with all of life's tests and trials (and some that the enemy has thrown in, too). When the marriage relationship has not been a priority, you grow apart.
One thing I have found to be true is that circumstances will come and go, but through it all, good and bad, my husband will always be right there beside me. Whether it is a life circumstance or a relationship issue, we know that with God, we can work through anything. And believe me, it only gets better!!
Last, but certainly not least, keep Christ in the very center of your marriage!
God Bless!!
Dawn
Shining brightly for Jesus