Why should marriage last forever?

Marriage with time a limit, I wonder what the vow is like, "Till our time has expired together": Why should marriage last forever? - Gender Roles - Salon.com:

How different might the experience of marriage be if both participants in it were subject to periodic, mutual review? The chance to say, here’s what’s working, here’s what’s changed, here’s what needs improvement? The opportunity, even, to say, maybe it’s time to move on? Why not acknowledge that a great five-year run could be more satisfying than a 30-year sentence? After all, we leave jobs and houses and quietly distance ourselves from old friends all the time, and it’s rarely considered failure.