Someone I know is going through a horrible time. He just found out that his wife has had enough of the relationship. She's been thinking about leaving for 5 years now but has never communicated this to him. They have built a solid foundation together: kids, property, businesses, homes, kids (8 and 9), friends, etc. I don't know the entire situation but I think that she didn't feel together with him anymore. He thought that she was happy.
It is truly hard to maintain years and years of a relationship (that "foreverness") with someone and still have that excellent communication and togetherness. I know this one couple where after 20 years of marriage, decided to part seperate ways.
There seems to be no secret magic or formula to make lasting relationships.
But, I heard this one old couple (of many years of happy marriage) say "We hold hands together before we fall asleep together everyday." That was their secret to a lasting marriage.