With the adoption of hanaflower's caveat about certain things, I agree with you, BK.
The whole ppoint of human expeience is that we grow and adpat to rise to the challenge of new experiences. Of course the advent of twins should affect the golf fixtures calendar. Of course expectations of all sorts of things should change as circumstnaces change.
BUT if , for example, you always knew that TomDickHarry was a gambler, or very lazy, or a hyper-energetic workaholilc, then you might expect not to be surprised when they apply that trait to everything they do subsequently.
In a sensible relationship between people with no fatal character flaws I would expect them to change, negotiate, compromise, be flexible with each other, respond to need, rise to challenges, and generally accept that certain things just need someone to say 'oh well, that changes everything'. Otherwise, as you say, how would partnership ever survive children - let alone something like a partner disabled, or ill, or needing to re-locate to outer-mongolia for work.
So: I think some things you have to allow for as a given - TomDickHarry is highly-strung, say, and do your best to try and predict how that might affect future life-events, and live with the 'highly-strungness' of their respnses...and other things - like golf - you can expect that a sensible father would relinquish, or downplay.
Also - how can a relationship get better (hollow laughter - talking theory here...) if no-one changes or grows or re-adjusts their priorities around joint circumstances?