A Ship (4 of 5?): Normal.

From the same, p. 174:

Though this last phase is also considered normal, society definitely neither advocates or condones it - in fact, scarcely acknowledges its existence. In this stage teh couple becomes disillusioned, bored, miserable, and ripe either for "breakup" or coma.

"Who said this progression is 'normal,' that this is the shape of love?" I asked myself. "And who decided what constitutes 'the real world'? The same guys who brought you Vietnam, Hustler, chicken factories, and an ozone layer that rivals swiss cheese," I replied...

. . .