What about people that are not in a long-distance relationship? Don’t they eventually get bored of seeing each other all the time? And those that are married?
Relationships (be it with your family, friends, spouse, SO) don’t remain in a constant state…there will be highs and lows. It takes the efforts of both parties to make it work. And I feel that some amount of space or distance is healthy for all relationships.
As to whether LD relationships work…some do and some dont…as is the case with all other types of relationships. You try your best…and in the end it’s whatever is in your kismat.