Here are some of my thoughts on the issue:
I imagine that if marriage would last for this life only, it would be of no eternal consequence.
Lately, I have been thinking a little bit about Christ's relationship with us as His people. Many times throughout the scriptures we hear that as a people, we are the bride, and Christ is the bridegroom.
“For thy Maker is thine husband; the Lord of hosts is his name” (Isa. 54:5)
"I sware unto thee, and entered into a covenant with thee, saith the Lord God, and thou becamest mine." (Ezek. 16:8)
To me, just by rights of comparing our relationship with Christ to marriage shows that marriage is important. He entered into a covenant with us as a people that if we will obey, we will become "joint-heirs with Christ...that we may be also glorified together." (Rom. 8:17) This covenant is everlasting. If marriage were not everlasting as well, why would He compare something as powerful as our relationship with Him to something so weak that it will not last beyond this life? In my mind, marriage must be as eternal as our relationship with Christ is to be.