Caroline & Mssrs Padfoot & Prongs
It should still hold if they die, though obviously it hasn't been tested, and hopefully never will. If they are physically here in this universe, the spell should hold. Don't know about other dimensions, like Asgard. I like to think it'd hold, but again, not tested. What should happen if someone dies is that it goes into the red, for danger, and stays there. I suppose eventually it'd go grey, once their body, er, ceases to exist in some way.