Well... i gathered a few thoughts after i last posted here. Here goes:
Considering that a magical effect can be made permanent, which means it actually
will last longer than the caster's death ("death" as in "ceasing to be alive", therefore liches and such are not included in this definition
), i see no reason why a spell cast, whichever it is, won't subside to the end of it's duration after the caster's death, unless explicitly stated otherwise.
However, regarding the rules for sharing spells with animal companions (and familiars, BTW), to keep it simple, i'd rule that the spell ceases to affect the companion/familiar. You can see it as if the essence/soul/consciousness of the caster left his/her body and headed towards the plane of the favored deity.
This way, it doesn't matter if there's only a finger, a tooth, a nail or dust left of the caster.
Also, would you rule that the caster is 5ft away, if the companion/familiar goes around with a lock of hair of the caster tied around it's neck? I wouldn't!