Do relationships change over time?

Yes. We change over time, it's only normal for relationship to change as we change. The level of intimacy might change, if you have children, children will change the relationship as well. There are many facets of the relationships, while some might seem static, some will change.
Yes. When people either develop or stagnate over time or both, invariably the relationship will change. In a positive sense one could think of this as growing old WITH someone. In a negative sense, on could think of this as growing old BECAUSE of someone.
Relationships. We all change over time to some degree, hopefully we grow together psychologically and spiritually. Health relationships allow for costive change which make relationships more interesting and growth promoting. Best.