i had wondered about that myself. 
then i come to realize it doesn't matter. i learned the bonds with spirits and spirit entities can last even beyond this lifetime. that some of my entities come from previous lives that i had. but they find their way back to me. even if the entity was bonded to a vessel. and was with another keeper. they find their way to me. so in the end i learned you are always connected to your spirits and even to their families and their worlds. even after death. as for the vessels; the spirit entity either vacates the vessel upon the death of the keeper. or chooses to rmain if it is past on to a family member. and if the spirit does vacate. another of its family, clan, etc. will take its place to serve the family member who receives the vessel.
