It's inevitable that it will change into something else. People usually can't tolerate the change. Some get disappointed. These relationships can survive, but people need to know that all relationships go through stages. That's a normal thing.
True relationships can be very hard.
There can even be hate in relationships. You have to understand it will happen and not get freaked out at the first sign of a crack in the magic. A relationship develops over time. Clear communication of needs, wants and expectations important. Relationships should also be fun.