Hardly, at least in the neck of the woods I come from.
My grandfather and grandmother were married for over 40 years before my grandmother died.
My mother and father were married for over 25 years before my father died.
My wife and I have been married over 20 years now.
My brother and his wife have been married over 21 years now.
My sister has been married over 10 years now, (13 years younger than me).
Many of my relatives, on both sides of the family, have been married for 20, 30, 40, 50 years or more.
Mythical? Where I come from it's the norm.