As crazy as it sounds, I do the same. But mostly for my mother. I wait every day/night to see if my dad calls me, telling me they fought and triggered my mom to collapse. Hasn't happened yet. But, hey, I never know when it will. I think it will numb me, but you are right. We won't be prepared for that moment. No matter how much we expect it.
i still don't think I'm ready for that happening, even until today.