See many Mnet threads passim.
No, IMHO.
The marriage ceremony does not fix the relationship in amber, making it immutable evermore. In fact, the marriage vows are designed to illustrate the potential for change during the marriage, e.g. in sickness and in health, for better for worse, for richer for poorer etc.
IMO, a marriage requires continuous renegotiation and redefinition in the face of life changes - the most relevant example to Mumsnetters is of course the arrival of children.
So - "you knew the score when you married..." is not a valid reason to cling to the status quo when the circumstances require change.
Discuss.