Re: Defining long term success
There are - or can be - various measures of success. Time - IMO - is not necessarily one of them.
In the past, marriage was primarily about property and progeny - in other words, inheritance and ensuring family wealth and continuity. So, if a marriage produced heirs, increased/maintained assets/influence, it was considered a success. Happiness and love between the spouses wasn't necessarily a concern, but a pleasant bonus.
In recent time, marriage is more about love in addition to the traditional goals of property and progeny. If you have a number of good years together, reach mutual goals, and experience some personal growth, then it's a success even if it ends soon or stressfully.
My first marriage was a long term success (we achieved our goals and produced successful offspring), even though it wasn't happy of fulfilling interpersonally. My second marriage is a greater success (goals; we were/are both past having children), and is also happy and fulfilling in every way.
Love is an ideal thing; marriage is a real thing; a confusion of the real with the ideal never goes unpunished. - Johann Wolfgang von Goethe
CELIBACY IS NOT HEREDITARY.