Judging by how fickle human emotions can be,and the way even couples who have even been married/living together for years have all of a sudden decided to split up and part ways, I'd say the whole act of growing old together, happily and still in love, would be a huge blessing indeed.

Personally I prefer to concentrate on the here and now, how I can better my marriage and indeed myself, and leave the future of my relationship to God and what He decrees to be best for me.