It's possible that you're both meant to die together.
Bonded as children, and then sex melded to booster the physical congress and telepathic link... That seems to have some expectations of permanence?
Besides it's poetic if you die because you spouse dies.
Stupid, but poetic.
Besides, they need to tackle over population somehow.
Although Sarek was married at least 4 times.
So, because of social mores, some spouses must chose not to unbond with their mate due to social conventions and expectations?